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Euclide PT, Larson WA, Shi Y, Gruenthal K, Christensen KA, Seeb J, Seeb L. Conserved islands of divergence associated with adaptive variation in sockeye salmon are maintained by multiple mechanisms. Mol Ecol 2023. [PMID: 37695544 DOI: 10.1111/mec.17126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 08/01/2023] [Accepted: 08/14/2023] [Indexed: 09/12/2023]
Abstract
Local adaptation is facilitated by loci clustered in relatively few regions of the genome, termed genomic islands of divergence. The mechanisms that create and maintain these islands and how they contribute to adaptive divergence is an active research topic. Here, we use sockeye salmon as a model to investigate both the mechanisms responsible for creating islands of divergence and the patterns of differentiation at these islands. Previous research suggested that multiple islands contributed to adaptive radiation of sockeye salmon. However, the low-density genomic methods used by these studies made it difficult to fully elucidate the mechanisms responsible for islands and connect genotypes to adaptive variation. We used whole genome resequencing to genotype millions of loci to investigate patterns of genetic variation at islands and the mechanisms that potentially created them. We discovered 64 islands, including 16 clustered in four genomic regions shared between two isolated populations. Characterisation of these four regions suggested that three were likely created by structural variation, while one was created by processes not involving structural variation. All four regions were small (< 600 kb), suggesting low recombination regions do not have to span megabases to be important for adaptive divergence. Differentiation at islands was not consistently associated with established population attributes. In sum, the landscape of adaptive divergence and the mechanisms that create it are complex; this complexity likely helps to facilitate fine-scale local adaptation unique to each population.
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Affiliation(s)
- Peter T Euclide
- Department of Forestry and Natural Resources, Illinois-Indiana Sea Grant, Purdue University, West Lafayette, Indiana, USA
| | - Wesley A Larson
- National Oceanographic and Atmospheric Administration, National Marine Fisheries Service, Alaska Fisheries Science Center, Auke Bay Laboratories, Juneau, Alaska, USA
| | - Yue Shi
- College of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Juneau, Alaska, USA
| | - Kristen Gruenthal
- Alaska Department of Fish and Game, Juneau, Alaska, USA
- Office of Applied Science, Wisconsin Department of Natural Resources, Wisconsin Cooperative Fishery Research Unit, College of Natural Resources, University of Wisconsin-Stevens Point, Stevens Point, Wisconsin, USA
| | - Kris A Christensen
- Department of Biology, University of Victoria, Victoria, British Columbia, Canada
| | - Jim Seeb
- School of Aquatic and Fishery Sciences, University of Washington, Seattle, Washington, USA
| | - Lisa Seeb
- School of Aquatic and Fishery Sciences, University of Washington, Seattle, Washington, USA
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Wilson EJ, Shedlock AM. Evaluating the Potential Fitness Effects of Chinook Salmon (Oncorhynchus tshawytscha) Aquaculture Using Non-Invasive Population Genomic Analyses of MHC Nucleotide Substitution Spectra. Animals (Basel) 2023; 13. [PMID: 36830380 DOI: 10.3390/ani13040593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 01/27/2023] [Accepted: 02/06/2023] [Indexed: 02/11/2023] Open
Abstract
Genetic diversity plays a vital role in the adaptability of salmon to changing environmental conditions that can introduce new selective pressures on populations. Variability among local subpopulations may increase the chance that certain advantageous genes are passed down to future generations to mitigate susceptibility to novel diseases, warming oceans, loss of genetic stocks, and ocean acidification. Class I and II genes of the major histocompatibility complex (MHC) are crucial for the fitness of Chinook salmon due to the role they play in disease and pathogen resistance. The objective of this study was to assess the DNA sequence variability among wild and hatchery populations of Alaskan Chinook salmon at the class I α1 and class II β1 exons of the MHC. We hypothesized that the 96 wild samples taken from the Deshka River would display greater levels of observed heterozygosity (Ho) relative to expected heterozygosity (He) in suggesting that individuals with similar phenotypes mate with one another more frequently than would be expected under random mating patterns. Conversely, since no mate selection occurs in the William Jack Hernandez Sport Fish hatchery, we would not expect to see this discrepancy (He = Ho) in the 96 hatchery fish tested in this study. Alternatively, we hypothesized that post-mating selection is driving higher levels of observed heterozygosity as opposed to mate selection. If this is the case, we will observe higher than expected levels of heterozygosity among hatchery salmon. Both populations displayed higher levels of observed heterozygosity than expected heterozygosity at the Class I and II loci but genetic differentiation between the spatially distinct communities was minimal. Class I sequences showed evidence of balancing selection, despite high rates of non-synonymous substitutions observed, specifically at the peptide binding regions of both MHC genes.
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3
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Lam DK, Frantz AC, Burke T, Geffen E, Sin SYW. Both selection and drift drive the spatial pattern of adaptive genetic variation in a wild mammal. Evolution 2023; 77:221-238. [PMID: 36626810 DOI: 10.1093/evolut/qpac014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2021] [Revised: 10/03/2022] [Accepted: 11/04/2022] [Indexed: 01/12/2023]
Abstract
The major histocompatibility complex (MHC) has been intensively studied for the relative effects of different evolutionary forces in recent decades. Pathogen-mediated balancing selection is generally thought to explain the high polymorphism observed in MHC genes, but it is still unclear to what extent MHC diversity is shaped by selection relative to neutral drift. In this study, we genotyped MHC class II DRB genes and 15 neutral microsatellite loci across 26 geographic populations of European badgers (Meles meles) covering most of their geographic range. By comparing variation of microsatellite and diversity of MHC at different levels, we demonstrate that both balancing selection and drift have shaped the evolution of MHC genes. When only MHC allelic identity was investigated, the spatial pattern of MHC variation was similar to that of microsatellites. By contrast, when functional aspects of the MHC diversity (e.g., immunological supertypes) were considered, balancing selection appears to decrease genetic structuring across populations. Our comprehensive sampling and analytical approach enable us to conclude that the likely mechanisms of selection are heterozygote advantage and/or rare-allele advantage. This study is a clear demonstration of how both balancing selection and genetic drift simultaneously affect the evolution of MHC genes in a widely distributed wild mammal.
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Affiliation(s)
- Derek Kong Lam
- School of Biological Sciences, The University of Hong Kong, Hong Kong, China
| | - Alain C Frantz
- Musée National d'Histoire Naturelle, Luxembourg, Luxembourg
| | - Terry Burke
- Ecology and Evolutionary Biology, School of Biosciences, University of Sheffield, Sheffield, United Kingdom
| | - Eli Geffen
- School of Zoology, Tel Aviv University, Tel Aviv, Israel
| | - Simon Yung Wa Sin
- School of Biological Sciences, The University of Hong Kong, Hong Kong, China
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4
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Li X, Liu T, Li A, Xiao Y, Sun K, Feng J. Diversifying selection and climatic effects on major histocompatibility complex class
II
gene diversity in the greater horseshoe bat. Evol Appl 2023; 16:688-704. [PMID: 36969140 PMCID: PMC10033860 DOI: 10.1111/eva.13528] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2022] [Revised: 12/19/2022] [Accepted: 12/21/2022] [Indexed: 01/09/2023] Open
Abstract
Heterogeneous pathogenic stress can shape major histocompatibility complex (MHC) diversity by influencing the functional plasticity of the immune response. Therefore, MHC diversity could reflect environmental stress, demonstrating its importance in uncovering the mechanisms of adaptive genetic variation. In this study, we combined neutral microsatellite loci, an immune-related MHC II-DRB locus, and climatic factors to unravel the mechanisms affecting the diversity and genetic differentiation of MHC genes in the greater horseshoe bat (Rhinolophus ferrumequinum), a species with a wide geographical distribution that has three distinct genetic lineages in China. First, increased genetic differentiation at the MHC locus among populations compared using microsatellites indicated diversifying selection. Second, the genetic differentiation of MHC and microsatellites were significantly correlated, suggesting that demographic processes exist. However, MHC genetic differentiation was significantly correlated with geographical distance among populations, even after controlling for the neutral markers, suggesting a major effect of selection. Third, although the MHC genetic differentiation was larger than that for microsatellites, there was no significant difference in the genetic differentiation between the two markers among genetic lineages, indicating the effect of balancing selection. Fourth, combined with climatic factors, MHC diversity and supertypes showed significant correlations with temperature and precipitation, but not with the phylogeographic structure of R. ferrumequinum, suggesting an effect of local adaptation driven by climate on MHC diversity. Moreover, the number of MHC supertypes varied between populations and lineages, suggesting regional characteristics and support for local adaptation. Taken together, the results of our study provide insights into the adaptive evolutionary driving forces at different geographic scales in R. ferrumequinum. In addition, climate factors may have played a vital role in driving adaptive evolution in this species.
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Affiliation(s)
- Xiaolin Li
- Jilin Provincial Key Laboratory of Animal Resource Conservation and Utilization Northeast Normal University Changchun China
- Key Laboratory of Vegetation Ecology, Ministry of Education Changchun China
| | - Tong Liu
- College of Life Science, Jilin Agricultural University Changchun China
| | - Aoqiang Li
- Jilin Provincial Key Laboratory of Animal Resource Conservation and Utilization Northeast Normal University Changchun China
| | - Yanhong Xiao
- Jilin Provincial Key Laboratory of Animal Resource Conservation and Utilization Northeast Normal University Changchun China
| | - Keping Sun
- Jilin Provincial Key Laboratory of Animal Resource Conservation and Utilization Northeast Normal University Changchun China
- Key Laboratory of Vegetation Ecology, Ministry of Education Changchun China
| | - Jiang Feng
- Jilin Provincial Key Laboratory of Animal Resource Conservation and Utilization Northeast Normal University Changchun China
- College of Life Science, Jilin Agricultural University Changchun China
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5
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Loh Z, Huan X, Awate S, Schrittwieser M, Renia L, Ren EC. Molecular Characterization of MHC Class I Alpha 1 and 2 Domains in Asian Seabass (Lates calcarifer). Int J Mol Sci 2022; 23:10688. [PMID: 36142628 PMCID: PMC9500968 DOI: 10.3390/ijms231810688] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Revised: 09/06/2022] [Accepted: 09/12/2022] [Indexed: 11/25/2022] Open
Abstract
The Asian seabass is of importance both as a farmed and wild animal. With the emergence of infectious diseases, there is a need to understand and characterize the immune system. In humans, the highly polymorphic MHC class I (MHC-I) molecules play an important role in antigen presentation for the adaptive immune system. In the present study, we characterized a single MHC-I gene in Asian seabass (Lates calcarifer) by amplifying and sequencing the MHC-I alpha 1 and alpha 2 domains, followed by multi-sequence alignment analyses. The results indicated that the Asian seabass MHC-I α1 and α2 domain sequences showed an overall similarity within Asian seabass and retained the majority of the conserved binding residues of human leukocyte antigen-A2 (HLA-A2). Phylogenetic tree analysis revealed that the sequences belonged to the U lineage. Mapping the conserved binding residue positions on human HLA-A2 and grass carp crystal structure showed a high degree of similarity. In conclusion, the availability of MHC-I α1 and α2 sequences enhances the quality of MHC class I genetic information in Asian seabass, providing new tools to analyze fish immune responses to pathogen infections, and will be applicable in the study of the phylogeny and the evolution of antigen-specific receptors.
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Talarico L, Marta S, Rossi AR, Crescenzo S, Petrosino G, Martinoli M, Tancioni L. Balancing selection, genetic drift, and human-mediated introgression interplay to shape MHC (functional) diversity in Mediterranean brown trout. Ecol Evol 2021; 11:10026-10041. [PMID: 34367556 PMCID: PMC8328470 DOI: 10.1002/ece3.7760] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Revised: 05/14/2021] [Accepted: 05/17/2021] [Indexed: 12/19/2022] Open
Abstract
The extraordinary polymorphism of major histocompatibility complex (MHC) genes is considered a paradigm of pathogen-mediated balancing selection, although empirical evidence is still scarce. Furthermore, the relative contribution of balancing selection to shape MHC population structure and diversity, compared to that of neutral forces, as well as its interaction with other evolutionary processes such as hybridization, remains largely unclear. To investigate these issues, we analyzed adaptive (MHC-DAB gene) and neutral (11 microsatellite loci) variation in 156 brown trout (Salmo trutta complex) from six wild populations in central Italy exposed to introgression from domestic hatchery lineages (assessed with the LDH gene). MHC diversity and structuring correlated with those at microsatellites, indicating the substantial role of neutral forces. However, individuals carrying locally rare MHC alleles/supertypes were in better body condition (a proxy of individual fitness/parasite load) regardless of the zygosity status and degree of sequence dissimilarity of MHC, hence supporting balancing selection under rare allele advantage, but not heterozygote advantage or divergent allele advantage. The association between specific MHC supertypes and body condition confirmed in part this finding. Across populations, MHC allelic richness increased with increasing admixture between native and domestic lineages, indicating introgression as a source of MHC variation. Furthermore, introgression across populations appeared more pronounced for MHC than microsatellites, possibly because initially rare MHC variants are expected to introgress more readily under rare allele advantage. Providing evidence for the complex interplay among neutral evolutionary forces, balancing selection, and human-mediated introgression in shaping the pattern of MHC (functional) variation, our findings contribute to a deeper understanding of the evolution of MHC genes in wild populations exposed to anthropogenic disturbance.
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Affiliation(s)
- Lorenzo Talarico
- Laboratory of Experimental Ecology and AquacultureDepartment of BiologyUniversity of Rome “Tor Vergata”RomeItaly
| | - Silvio Marta
- Department of Environmental Science and PolicyUniversity of MilanMilanItaly
| | - Anna Rita Rossi
- Department of Biology and Biotechnology C. DarwinUniversity of Rome “La Sapienza”RomeItaly
| | - Simone Crescenzo
- Department of Biology and Biotechnology C. DarwinUniversity of Rome “La Sapienza”RomeItaly
| | - Gerardo Petrosino
- Department of Biology and Biotechnology C. DarwinUniversity of Rome “La Sapienza”RomeItaly
| | - Marco Martinoli
- Laboratory of Experimental Ecology and AquacultureDepartment of BiologyUniversity of Rome “Tor Vergata”RomeItaly
- Consiglio per la Ricerca in Agricoltura e l'Analisi dell'Economia Agraria (CREA)Centro di Zootecnia e AcquacolturaMonterotondoItaly
| | - Lorenzo Tancioni
- Laboratory of Experimental Ecology and AquacultureDepartment of BiologyUniversity of Rome “Tor Vergata”RomeItaly
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7
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Talarico L, Babik W, Marta S, Pietrocini V, Mattoccia M. MHC structuring and divergent allele advantage in a urodele amphibian: a hierarchical multi-scale approach. Heredity (Edinb) 2019; 123:593-607. [PMID: 31036951 PMCID: PMC6972932 DOI: 10.1038/s41437-019-0221-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Revised: 03/31/2019] [Accepted: 03/31/2019] [Indexed: 12/27/2022] Open
Abstract
Proteins encoded by extraordinarily polymorphic major histocompatibility complex (MHC) genes are involved in the adaptive immune response. Balancing selection is believed to maintain MHC polymorphism in the long term, although neutral processes also play a role in shaping MHC diversity. However, the relative contribution of these processes is poorly understood. Here we characterized MHC class II variation of a low-dispersal, pond-breeding newt (Triturus carnifex) over a restricted, geographically structured area. We aimed to (1) evaluate the contribution of selection and neutral processes to shaping MHC diversity at two geographic scales, and (2) test for signatures of divergent allele advantage (DAA), which is a potentially important mechanism of balancing selection. The dominant role of selection in shaping MHC variation was suggested by the lack of correlation between MHC and neutral (microsatellite) variation. Although most variation occurred within populations for both types of markers, they differed in the extent of structuring at the two spatial scales. MHC structuring was more pronounced at local scales, suggesting the role of local selection, while structuring was not detectable at a larger scale, possibly due to the effect of balancing selection. Microsatellites showed the opposite pattern. As expected under DAA, the observed genotypes combined more sequence diversity than expected under a random association of alleles. Thus, DAA may contribute to maintaining MHC polymorphism, which is ancient, as supported by signatures of historical positive selection and trans-species polymorphism. Our results point to the importance of a multi-scale approach in studying MHC variation, especially in low-dispersal taxa, which are genetically structured at fine spatial scales.
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Affiliation(s)
- Lorenzo Talarico
- Department of Biology, University of Rome Tor Vergata, Via della Ricerca Scientifica 1, Rome, 00133, Italy.
| | - Wiesław Babik
- Institute of Environmental Sciences, Jagiellonian University, Gronostajowa 7, Kraków, 30-387, Poland
| | - Silvio Marta
- Department of Environmental Sciences and Policy, University of Milan, Via G. Celoria 26, Milan, 20133, Italy
| | - Venusta Pietrocini
- Department of Biology, University of Rome Tor Vergata, Via della Ricerca Scientifica 1, Rome, 00133, Italy
| | - Marco Mattoccia
- Department of Biology, University of Rome Tor Vergata, Via della Ricerca Scientifica 1, Rome, 00133, Italy
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8
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Jeffries KM, Connon RE, Verhille CE, Dabruzzi TF, Britton MT, Durbin‐Johnson BP, Fangue NA. Divergent transcriptomic signatures in response to salinity exposure in two populations of an estuarine fish. Evol Appl 2019; 12:1212-1226. [PMID: 31293632 PMCID: PMC6597873 DOI: 10.1111/eva.12799] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
In estuary and coastal systems, human demand for freshwater, climate change-driven precipitation variability, and extreme weather impact salinity levels, reducing connectivity between mesohaline coastal fish populations and potentially contributing to genomic divergence. We examined gill transcriptome responses to salinity in wild-caught juveniles from two populations of Sacramento splittail (Pogonichthys macrolepidotus), a species of conservation concern that is endemic to the San Francisco Estuary, USA, and the lower reaches of its tributaries. Recent extreme droughts have led to salinities above the tolerance limits for this species, creating a migration barrier between these populations, which potentially contributed to population divergence. We identified transcripts involved in a conserved response to salinity; however, the more salinity-tolerant San Pablo population had greater transcriptome plasticity (3.6-fold more transcripts responded than the Central Valley population) and a response consistent with gill remodeling after 168 hr of exposure to elevated salinity. The reorganization of the gill in response to changing osmotic gradients is a process critical for acclimation and would facilitate enhanced salinity tolerance. We detected an upregulation of receptors that control the Wnt (wingless-type) cell signaling pathway that may be required for an adaptive response to increases in salinity, patterns not observed in the relatively salinity-sensitive Central Valley population. We detected 62 single nucleotide polymorphisms (SNPs) in coding regions of 26 transcripts that differed between the populations. Eight transcripts that contained SNPs were associated with immune responses, highlighting the importance of diversity in immune gene sequences as a defining characteristic of genomic divergence between these populations. Our data demonstrate that these populations have divergent transcriptomic responses to salinity, which is consistent with observed physiological differences in salinity tolerance.
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Affiliation(s)
- Ken M. Jeffries
- Department of Biological SciencesUniversity of ManitobaWinnipegManitobaCanada
- Anatomy, Physiology & Cell Biology, School of Veterinary MedicineUniversity of CaliforniaDavisCalifornia
- Wildlife, Fish & Conservation BiologyUniversity of CaliforniaDavisCalifornia
| | - Richard E. Connon
- Anatomy, Physiology & Cell Biology, School of Veterinary MedicineUniversity of CaliforniaDavisCalifornia
| | - Christine E. Verhille
- Wildlife, Fish & Conservation BiologyUniversity of CaliforniaDavisCalifornia
- Present address:
Department of EcologyMontana State UniversityBozemanMontana
| | - Theresa F. Dabruzzi
- Wildlife, Fish & Conservation BiologyUniversity of CaliforniaDavisCalifornia
- Present address:
Biology DepartmentSaint Anselm CollegeManchesterNew Hampshire
| | - Monica T. Britton
- Bioinformatics Core Facility, Genome CenterUniversity of CaliforniaDavisCalifornia
| | | | - Nann A. Fangue
- Wildlife, Fish & Conservation BiologyUniversity of CaliforniaDavisCalifornia
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9
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Larson WA, Dann TH, Limborg MT, McKinney GJ, Seeb JE, Seeb LW. Parallel signatures of selection at genomic islands of divergence and the major histocompatibility complex in ecotypes of sockeye salmon across Alaska. Mol Ecol 2019; 28:2254-2271. [DOI: 10.1111/mec.15082] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Revised: 02/21/2019] [Accepted: 03/20/2019] [Indexed: 12/31/2022]
Affiliation(s)
- Wesley A. Larson
- School of Aquatic and Fishery Sciences University of Washington Seattle Washington
| | - Tyler H. Dann
- School of Aquatic and Fishery Sciences University of Washington Seattle Washington
- Gene Conservation Laboratory Alaska Department of Fish and Game Anchorage Alaska
| | - Morten T. Limborg
- School of Aquatic and Fishery Sciences University of Washington Seattle Washington
| | - Garrett J. McKinney
- School of Aquatic and Fishery Sciences University of Washington Seattle Washington
| | - James E. Seeb
- School of Aquatic and Fishery Sciences University of Washington Seattle Washington
| | - Lisa W. Seeb
- School of Aquatic and Fishery Sciences University of Washington Seattle Washington
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10
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Khrustaleva AM. Inferring Adaptive Nature of Major Histocompatibility Complex (MHC) Polymorphism from Single Nucleotide Substitutions in Asian Sockeye Salmon Populations: II. Factors Determining Onne-DAB Gene Variability in the Kamchatka River Basin. RUSS J GENET+ 2018. [DOI: 10.1134/s102279541811008x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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11
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Khrustaleva AM, Ponomareva EV, Ponomareva MV, Shubina EA, Uglova TY, Klovach NV. Inferring Adaptive Nature of Major Histocompatibility Complex (MHC) Polymorphism from Single Nucleotide Substitutions in Asian Sockeye Salmon Populations: I. Different Forms of Selection Act in Sockeye Salmon Populations from the Ozernaya and Kamchatka Rivers. RUSS J GENET+ 2018. [DOI: 10.1134/s1022795418100071] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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12
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Heimeier D, Alexander A, Hamner RM, Pichler F, Baker CS. The Influence of Selection on MHC DQA and DQB Haplotypes in the Endemic New Zealand Hector’s and Māui Dolphins. J Hered 2018; 109:744-756. [DOI: 10.1093/jhered/esy050] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Accepted: 09/19/2018] [Indexed: 01/15/2023] Open
Affiliation(s)
- Dorothea Heimeier
- School of Biological Sciences, University of Auckland, Private Bag, Auckland, New Zealand
| | - Alana Alexander
- Biodiversity Institute, University of Kansas, Jayhawk Boulevard, Lawrence, KS
| | - Rebecca M Hamner
- Marine Mammal Institute and Department of Fisheries and Wildlife, Hatfield Marine Science Center, Oregon State University, SE Marine Science Drive, Newport, OR
- School of Biological Sciences, University of Auckland, Private Bag, Auckland, New Zealand
| | - Franz Pichler
- School of Biological Sciences, University of Auckland, Private Bag, Auckland, New Zealand
| | - C Scott Baker
- Marine Mammal Institute and Department of Fisheries and Wildlife, Hatfield Marine Science Center, Oregon State University, SE Marine Science Drive, Newport, OR
- School of Biological Sciences, University of Auckland, Private Bag, Auckland, New Zealand
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13
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Pearson SK, Bull CM, Gardner MG. Selection outweighs drift at a fine scale: Lack of MHC differentiation within a family living lizard across geographically close but disconnected rocky outcrops. Mol Ecol 2018; 27:2204-2214. [PMID: 29603473 DOI: 10.1111/mec.14571] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2017] [Revised: 02/26/2018] [Accepted: 03/01/2018] [Indexed: 11/30/2022]
Abstract
The highly polymorphic genes of the major histocompatibility complex (MHC) are involved in disease resistance, mate choice and kin recognition. Therefore, they are widely used markers for investigating adaptive variation. Although selection is the key driver, gene flow and genetic drift also influence adaptive genetic variation, sometimes in opposing ways and with consequences for adaptive potential. To further understand the processes that generate MHC variation, it is helpful to compare variation at the MHC with that at neutral genetic loci. Differences in MHC and neutral genetic variation are useful for inferring the relative influence of selection, gene flow and drift on MHC variation. To date, such investigations have usually been undertaken at a broad spatial scale. Yet, evolutionary and ecological processes can occur at a fine spatial scale, particularly in small or fragmented populations. We investigated spatial patterns of MHC variation among three geographically close, naturally discrete, sampling sites of Egernia stokesii, an Australian lizard. The MHC of E. stokesii has recently been characterized, and there is evidence for historical selection on the MHC. We found E. stokesii MHC weakly differentiated among sites compared to microsatellites, suggesting selection, acting similarly at each site, has outweighed any effects of low gene flow or of genetic drift on E. stokesii MHC variation. Our findings demonstrate the strength of selection in shaping patterns of MHC variation or consistency at a fine spatial scale.
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Affiliation(s)
- Sarah K Pearson
- College of Science and Engineering, Flinders University, Bedford Park, SA, Australia
| | - C Michael Bull
- College of Science and Engineering, Flinders University, Bedford Park, SA, Australia
| | - Michael G Gardner
- College of Science and Engineering, Flinders University, Bedford Park, SA, Australia.,Evolutionary Biology Unit, South Australian Museum, Adelaide, SA, Australia
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14
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Gordeeva NV, Salmenkova EA. Genetic markers of adaptive processes in the Far Eastern pink salmon Oncorhynchus gorbuscha: Allelic diversity at the locus of major histocompatibility complex MHC I-A1. RUSS J GENET+ 2017. [DOI: 10.1134/s1022795417110035] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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15
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Parmar DR, Mitra S, Bhadouriya S, Rao T, Kunteepuram V, Gaur A. Characterization of major histocompatibility complex class I, and class II DRB loci of captive and wild Indian leopards (Panthera pardus fusca). Genetica 2017; 145:541-58. [DOI: 10.1007/s10709-017-9979-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 08/14/2017] [Indexed: 10/19/2022]
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16
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Baillie SM, Hemstock RR, Muir AM, Krueger CC, Bentzen P. Small-scale intraspecific patterns of adaptive immunogenetic polymorphisms and neutral variation in Lake Superior lake trout. Immunogenetics 2018; 70:53-66. [PMID: 28547520 DOI: 10.1007/s00251-017-0996-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Accepted: 04/26/2017] [Indexed: 10/19/2022]
Abstract
Many fishes express high levels of intraspecific variability, often linked to resource partitioning. Several studies show that a species' evolutionary trajectory of adaptive divergence can undergo reversals caused by changes in its environment. Such a reversal in neutral genetic and morphological variation among lake trout Salvelinus namaycush ecomorphs appears to be underway in Lake Superior. However, a water depth gradient in neutral genetic divergence was found to be associated with intraspecific diversity in the lake. To investigate patterns of adaptive immunogenetic variation among lake trout ecomorphs, we used Illumina high-throughput sequencing. The population's genetic structure of the major histocompatibility complex (MHC Class IIβ exon 2) and 18 microsatellite loci were compared to disentangle neutral and selective processes at a small geographic scale. Both MHC and microsatellite variation were partitioned more by water depth stratum than by ecomorph. Several metrics showed strong clustering by water depth in MHC alleles, but not microsatellites. We report a 75% increase in the number of MHC alleles shared between the predominant shallow and deep water ecomorphs since a previous lake trout MHC study at the same locale (c. 1990s data). This result is consistent with the reverse speciation hypothesis, although adaptive MHC polymorphisms persist along an ecological gradient. Finally, results suggested that the lake trout have multiple copies of the MHC II locus consistent with a historic genomic duplication event. Our findings indicated that conservation approaches for this species could focus on managing various ecological habitats by depth, in addition to regulating the fisheries specific to ecomorphs.
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Ciborowski K, Jordan WC, Garcia de Leaniz C, Consuegra S. Temporal and spatial instability in neutral and adaptive (MHC) genetic variation in marginal salmon populations. Sci Rep 2017; 7:42416. [PMID: 28186200 DOI: 10.1038/srep42416] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Accepted: 01/10/2017] [Indexed: 12/04/2022] Open
Abstract
The role of marginal populations for the long-term maintenance of species’ genetic diversity and evolutionary potential is particularly timely in view of the range shifts caused by climate change. The Centre-Periphery hypothesis predicts that marginal populations should bear reduced genetic diversity and have low evolutionary potential. We analysed temporal stability at neutral microsatellite and adaptive MHC genetic variation over five decades in four marginal Atlantic salmon populations located at the southern limit of the species’ distribution with a complicated demographic history, which includes stocking with foreign and native salmon for at least 2 decades. We found a temporal increase in neutral genetic variation, as well as temporal instability in population structuring, highlighting the importance of temporal analyses in studies that examine the genetic diversity of peripheral populations at the margins of the species’ range, particularly in face of climate change.
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Larson WA, Limborg MT, McKinney GJ, Schindler DE, Seeb JE, Seeb LW. Genomic islands of divergence linked to ecotypic variation in sockeye salmon. Mol Ecol 2016; 26:554-570. [PMID: 27864910 DOI: 10.1111/mec.13933] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 10/14/2016] [Accepted: 10/25/2016] [Indexed: 12/14/2022]
Abstract
Regions of the genome displaying elevated differentiation (genomic islands of divergence) are thought to play an important role in local adaptation, especially in populations experiencing high gene flow. However, the characteristics of these islands as well as the functional significance of genes located within them remain largely unknown. Here, we used data from thousands of SNPs aligned to a linkage map to investigate genomic islands of divergence in three ecotypes of sockeye salmon (Oncorhynchus nerka) from a single drainage in southwestern Alaska. We found ten islands displaying high differentiation among ecotypes. Conversely, neutral structure observed throughout the rest of the genome was low and not partitioned by ecotype. One island on linkage group So13 was particularly large and contained six SNPs with FST > 0.14 (average FST of neutral SNPs = 0.01). Functional annotation revealed that the peak of this island contained a nonsynonymous mutation in a gene involved in growth in other species (TULP4). The islands that we discovered were relatively small (80-402 Kb), loci found in islands did not show reduced levels of diversity, and loci in islands displayed slightly elevated linkage disequilibrium. These attributes suggest that the islands discovered here were likely generated by divergence hitchhiking; however, we cannot rule out the possibility that other mechanisms may have produced them. Our results suggest that islands of divergence serve an important role in local adaptation with gene flow and represent a significant advance towards understanding the genetic basis of ecotypic differentiation.
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Affiliation(s)
- Wesley A Larson
- School of Aquatic and Fishery Sciences, University of Washington, 1122 NE Boat Street, Box 355020, Seattle, WA, 98195-5020, USA
| | - Morten T Limborg
- School of Aquatic and Fishery Sciences, University of Washington, 1122 NE Boat Street, Box 355020, Seattle, WA, 98195-5020, USA
| | - Garrett J McKinney
- School of Aquatic and Fishery Sciences, University of Washington, 1122 NE Boat Street, Box 355020, Seattle, WA, 98195-5020, USA
| | - Daniel E Schindler
- School of Aquatic and Fishery Sciences, University of Washington, 1122 NE Boat Street, Box 355020, Seattle, WA, 98195-5020, USA
| | - James E Seeb
- School of Aquatic and Fishery Sciences, University of Washington, 1122 NE Boat Street, Box 355020, Seattle, WA, 98195-5020, USA
| | - Lisa W Seeb
- School of Aquatic and Fishery Sciences, University of Washington, 1122 NE Boat Street, Box 355020, Seattle, WA, 98195-5020, USA
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Garvin MR, Templin WD, Gharrett AJ, DeCovich N, Kondzela CM, Guyon JR, McPhee MV. Potentially adaptive mitochondrial haplotypes as a tool to identify divergent nuclear loci. Methods Ecol Evol 2016. [DOI: 10.1111/2041-210x.12698] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Michael R. Garvin
- Oregon State University Ringgold Standard Institution ‐ Integrative Biology 3029 Cordley Hall, 2701 SW Campus Way Corvallis OR 97331‐4501 USA
| | - William D. Templin
- Alaska Department of Fish and Game Division of Commercial Fisheries 333 Raspberry Road Anchorage AK 99518 USA
| | - Anthony J. Gharrett
- University of Alaska Fairbanks College Fisheries and Ocean Sciences Juneau AK 99821 USA
| | - Nick DeCovich
- Alaska Department of Fish and Game Division of Commercial Fisheries 333 Raspberry Road Anchorage AK 99518 USA
| | - Christine M. Kondzela
- Auke Bay Laboratories Alaska Fisheries Science Center National Oceanic and Atmospheric Administration National Marine Fisheries Service 17109 Point Lena Loop Road Juneau AK 99801 USA
| | - Jeffrey R. Guyon
- Auke Bay Laboratories Alaska Fisheries Science Center National Oceanic and Atmospheric Administration National Marine Fisheries Service 17109 Point Lena Loop Road Juneau AK 99801 USA
| | - Megan V. McPhee
- University of Alaska Fairbanks College Fisheries and Ocean Sciences Juneau AK 99821 USA
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Larson WA, Lisi PJ, Seeb JE, Seeb LW, Schindler DE. Major histocompatibility complex diversity is positively associated with stream water temperatures in proximate populations of sockeye salmon. J Evol Biol 2016; 29:1846-59. [PMID: 27341174 DOI: 10.1111/jeb.12926] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Revised: 06/16/2016] [Accepted: 06/23/2016] [Indexed: 01/16/2023]
Abstract
Local adaptation to heterogeneous environments generates population diversity within species, significantly increasing ecosystem stability and flows of ecosystem services. However, few studies have isolated the specific mechanisms that create and maintain this diversity. Here, we examined the relationship between water temperature in streams used for spawning and genetic diversity at a gene involved in immune function [the major histocompatibility complex (MHC)] in 14 populations of sockeye salmon (Oncorhynchus nerka) sampled across the Wood River basin in south-western Alaska. The largest influence on MHC diversity was lake basin, but we also found a significant positive correlation between average water temperature and MHC diversity. This positive relationship between temperature and MHC diversity appears to have been produced by natural selection at very local scales rather than neutral processes, as no correlation was observed between temperature and genetic diversity at 90 neutral markers. Additionally, no significant relationship was observed between temperature variability and MHC diversity. Although lake basin was the largest driver of differences in MHC diversity, our results also demonstrate that fine-scale differences in water temperature may generate variable selection regimes in populations that spawn in habitats separated by as little as 1 km. Additionally, our results indicated that some populations may be reaching a maximum level of MHC diversity. We postulate that salmon from populations in warm streams may delay spawning until late summer to avoid thermal stress as well as the elevated levels of pathogen prevalence and virulence associated with warm temperatures earlier in the summer.
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Affiliation(s)
- W A Larson
- School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA, USA.
| | - P J Lisi
- School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA, USA
| | - J E Seeb
- School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA, USA
| | - L W Seeb
- School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA, USA
| | - D E Schindler
- School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA, USA
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Zeng QQ, He K, Sun DD, Ma MY, Ge YF, Fang SG, Wan QH. Balancing selection and recombination as evolutionary forces caused population genetic variations in golden pheasant MHC class I genes. BMC Evol Biol 2016; 16:42. [PMID: 26892934 PMCID: PMC4758006 DOI: 10.1186/s12862-016-0609-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2015] [Accepted: 02/02/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The major histocompatibility complex (MHC) genes are vital partners in the acquired immune processes of vertebrates. MHC diversity may be directly associated with population resistance to infectious pathogens. Here, we screened for polymorphisms in exons 2 and 3 of the IA1 and IA2 genes in 12 golden pheasant populations across the Chinese mainland to characterize their genetic variation levels, to understand the effects of historical positive selection and recombination in shaping class I diversity, and to investigate the genetic structure of wild golden pheasant populations. RESULTS Among 339 individual pheasants, we identified 14 IA1 alleles in exon 2 (IA1-E2), 11 IA1-E3 alleles, 27 IA2-E2 alleles, and 28 IA2-E3 alleles. The non-synonymous substitution rate was significantly greater than the synonymous substitution rate at sequences in the IA2 gene encoding putative peptide-binding sites but not in the IA1 gene; we also found more positively selected sites in IA2 than in IA1. Frequent recombination events resulted in at least 9 recombinant IA2 alleles, in accordance with the intermingling pattern of the phylogenetic tree. Although some IA alleles are widely shared among studied populations, large variation occurs in the number of IA alleles across these populations. Allele frequency analysis across 2 IA loci showed low levels of genetic differentiation among populations on small geographic scales; however, significant genetic differentiation was observed between pheasants from the northern and southern regions of the Yangtze River. Both STRUCTURE analysis and F-statistic (F ST ) value comparison classified those populations into 2 major groups: the northern region of the Yangtze River (NYR) and the southern region of the Yangtze River (SYR). CONCLUSIONS More extensive polymorphisms in IA2 than IA1 indicate that IA2 has undergone much stronger positive-selection pressure during evolution. Moreover, the recombination events detected between the genes and the intermingled phylogenetic pattern indicate that interlocus recombination accounts for much of the allelic variation in IA2. Analysis of the population differentiation implied that homogenous balancing selection plays an important part in maintaining an even distribution of MHC variations. The natural barrier of the Yangtze River and heterogeneous balancing selection might help shape the NYR-SYR genetic structure in golden pheasants.
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Affiliation(s)
- Qian-Qian Zeng
- The Key Laboratory of Conservation Biology for Endangered Wildlife of the Ministry of Education, State Conservation Center for Gene Resources of Endangered Wildlife, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China.
| | - Ke He
- The Key Laboratory of Conservation Biology for Endangered Wildlife of the Ministry of Education, State Conservation Center for Gene Resources of Endangered Wildlife, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China.
- College of Animal Science and Technology, Zhejiang A&F University, Lin'an, Zhejiang, 311300, China.
| | - Dan-Dan Sun
- The Key Laboratory of Conservation Biology for Endangered Wildlife of the Ministry of Education, State Conservation Center for Gene Resources of Endangered Wildlife, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China.
| | - Mei-Ying Ma
- The Key Laboratory of Conservation Biology for Endangered Wildlife of the Ministry of Education, State Conservation Center for Gene Resources of Endangered Wildlife, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China.
| | - Yun-Fa Ge
- The Key Laboratory of Conservation Biology for Endangered Wildlife of the Ministry of Education, State Conservation Center for Gene Resources of Endangered Wildlife, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China.
| | - Sheng-Guo Fang
- The Key Laboratory of Conservation Biology for Endangered Wildlife of the Ministry of Education, State Conservation Center for Gene Resources of Endangered Wildlife, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China.
| | - Qiu-Hong Wan
- The Key Laboratory of Conservation Biology for Endangered Wildlife of the Ministry of Education, State Conservation Center for Gene Resources of Endangered Wildlife, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China.
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Seifertová M, Jarkovský J, Šimková A. Does the parasite-mediated selection drive the MHC class IIB diversity in wild populations of European chub (Squalius cephalus)? Parasitol Res 2015; 115:1401-15. [PMID: 26693717 DOI: 10.1007/s00436-015-4874-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 12/07/2015] [Indexed: 11/29/2022]
Abstract
The genes of major histocompatibility complex (MHC) provide an excellent opportunity to study host-parasite relationships because they are expected to evolve in response to parasites and variation in parasite communities. In this study, we investigated the potential role of parasite-mediated selection acting on MHC class IIB (DAB) genes in European chub (Squalius cephalus) natural populations. We found significant differences between populations in metazoan parasites, neutral and adaptive genetic diversities. The analyses based on pairwise data revealed that populations with dissimilar MHC allelic profiles were geographically distant populations with significantly different diversity in microsatellites and a dissimilar composition of parasite communities. The results from the generalized estimating equations method (GEE) on the level of individuals revealed that metazoan parasite load in European chub was influenced by the diversity of DAB alleles as well as by the diversity of neutral genetic markers and host traits reflecting condition and immunocompetence. The multivariate co-inertia analysis showed specific associations between DAB alleles and parasite species. DAB1-like alleles were more involved in associations with ectoparasites, while DAB3-like alleles were positively associated with endoparasites which could suggest potential differences between DAB genes caused by different selection pressure. Our study revealed that parasite-mediated selection is not the only variable affecting MHC diversity in European chub; however, we strongly support the role of neutral processes as the main driver of DAB diversity across populations. In addition, our study contributes to the understanding of the evolution of MHC genes in wild living fish.
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Affiliation(s)
- Mária Seifertová
- Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, 61137, Brno, Czech Republic.
| | - Jiří Jarkovský
- Institute of Biostatistics and Analyses, Faculty of Medicine and Faculty of Science, Masaryk University, Kamenice 126/3, 625 00, Brno, Czech Republic
| | - Andrea Šimková
- Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, 61137, Brno, Czech Republic
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Newhouse DJ, Balakrishnan CN. High major histocompatibility complex class I polymorphism despite bottlenecks in wild and domesticated populations of the zebra finch (Taeniopygia guttata). BMC Evol Biol 2015; 15:265. [PMID: 26627847 PMCID: PMC4667478 DOI: 10.1186/s12862-015-0546-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Accepted: 11/20/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Two subspecies of zebra finch, Taeniopygia guttata castanotis and T. g. guttata are native to Australia and the Lesser Sunda Islands, respectively. The Australian subspecies has been domesticated and is now an important model system for research. Both the Lesser Sundan subspecies and domesticated Australian zebra finches have undergone population bottlenecks in their history, and previous analyses using neutral markers have reported reduced neutral genetic diversity in these populations. Here we characterize patterns of variation in the third exon of the highly variable major histocompatibility complex (MHC) class I α chain. As a benchmark for neutral divergence, we also report the first mitochondrial NADH dehydrogenase 2 (ND2) sequences in this important model system. RESULTS Despite natural and human-mediated population bottlenecks, we find that high MHC class I polymorphism persists across all populations. As expected, we find higher levels of nucleotide diversity in the MHC locus relative to neutral loci, and strong evidence of positive selection acting on important residues forming the peptide-binding region (PBR). Clear population differentiation of MHC allele frequencies is also evident, and this may be due to adaptation to new habitats and associated pathogens and/or genetic drift. Whereas the MHC Class I locus shows broad haplotype sharing across populations, ND2 is the first locus surveyed to date to show reciprocal monophyly of the two subspecies. CONCLUSIONS Despite genetic bottlenecks and genetic drift, all surveyed zebra finch populations have maintained high MHC Class I diversity. The diversity at the MHC Class I locus in the Lesser Sundan subspecies contrasts sharply with the lack of diversity in previously examined neutral loci, and may thus be a result of selection acting to maintain polymorphism. Given uncertainty in historical population demography, however, it is difficult to rule out neutral processes in maintaining the observed diversity. The surveyed populations also differ in MHC Class I allele frequencies, and future studies are needed to assess whether these changes result in functional immune differences.
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Affiliation(s)
- Daniel J Newhouse
- Howell Science Complex, East Carolina University, Greenville, NC, 27858, USA.
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Stutz WE, Schmerer M, Coates JL, Bolnick DI. Among-lake reciprocal transplants induce convergent expression of immune genes in threespine stickleback. Mol Ecol 2015; 24:4629-46. [PMID: 26118468 DOI: 10.1111/mec.13295] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Revised: 06/22/2015] [Accepted: 06/24/2015] [Indexed: 12/25/2022]
Abstract
Geographic variation in parasite communities can drive evolutionary divergence in host immune genes. However, biotic and abiotic environmental variation can also induce plastic differences in immune function among populations. At present, there is little information concerning the relative magnitudes of heritable vs. induced immune divergence in natural populations. We examined immune gene expression profiles of threespine stickleback (Gasterosteus aculeatus) from six lakes on Vancouver Island, British Columbia. Parasite community composition differs between lake types (large or small, containing limnetic- or benthic-like stickleback) and between watersheds. We observed corresponding differences in immune gene expression profiles among wild-caught stickleback, using a set of seven immune genes representing distinct branches of the immune system. To evaluate the role of environmental effects on this differentiation, we experimentally transplanted wild-caught fish into cages in their native lake, or into a nearby foreign lake. Transplanted individuals' immune gene expression converged on patterns typical of their destination lake, deviating from their native expression profile. Transplant individuals' source population had a much smaller effect, suggesting relatively weak genetic underpinning of population differences in immunity, as viewed through gene expression. This strong environmental regulation of immune gene expression provides a counterpoint to the large emerging literature documenting microevolution and genetic diversification of immune function. Our findings illustrate the value of studying immunity in natural environmental settings where the immune system has evolved and actively functions.
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Affiliation(s)
- William E Stutz
- Department of Integrative Biology, University of Texas at Austin, One University Station C0990, Austin, TX, 78712, USA
| | - Matthew Schmerer
- Department of Integrative Biology, University of Texas at Austin, One University Station C0990, Austin, TX, 78712, USA
| | - Jessica L Coates
- Department of Biology, Spelman College, 350 Spelman Lane SW, Atlanta, GA, 30314, USA
| | - Daniel I Bolnick
- Department of Integrative Biology, University of Texas at Austin, One University Station C0990, Austin, TX, 78712, USA.,Howard Hughes Medical Institute, University of Texas at Austin, One University Station C0990, Austin, TX, 78712, USA
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25
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Fijarczyk A, Babik W. Detecting balancing selection in genomes: limits and prospects. Mol Ecol 2015; 24:3529-45. [DOI: 10.1111/mec.13226] [Citation(s) in RCA: 144] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Revised: 04/27/2015] [Accepted: 04/30/2015] [Indexed: 12/17/2022]
Affiliation(s)
- Anna Fijarczyk
- Institute of Environmental Sciences; Jagiellonian University; Gronostajowa 7 30-387 Kraków Poland
| | - Wiesław Babik
- Institute of Environmental Sciences; Jagiellonian University; Gronostajowa 7 30-387 Kraków Poland
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Bichet C, Moodley Y, Penn DJ, Sorci G, Garnier S. Genetic structure in insular and mainland populations of house sparrows (Passer domesticus) and their hemosporidian parasites. Ecol Evol 2015; 5:1639-52. [PMID: 25937907 PMCID: PMC4409412 DOI: 10.1002/ece3.1452] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 02/08/2015] [Indexed: 11/07/2022] Open
Abstract
Small and isolated populations usually exhibit low levels of genetic variability, and thus, they are expected to have a lower capacity to adapt to changes in environmental conditions, such as exposure to pathogens and parasites. Comparing the genetic variability of selectively neutral versus functional loci allows one to assess the evolutionary history of populations and their future evolutionary potential. The genes of the major histocompatibility complex (MHC) control immune recognition of parasites, and their unusually high diversity is genes which is likely driven by parasite-mediated balancing selection. Here, we examined diversity and differentiation of neutral microsatellite loci and functional MHC class I genes in house sparrows (Passer domesticus), living in six insular and six mainland populations, and we aimed to determine whether their diversity or differentiation correlates with the diversity and the prevalence of infection of hemosporidian parasites. We found that island bird populations tended to have lower neutral genetic variability, whereas MHC variability gene was similar between island and mainland populations. Similarly, island populations tended to show greater genetic differentiation than mainland populations, especially at microsatellite markers. The maintenance of MHC genetic diversity and its less marked structure in the island populations could be attributed to balancing-selection. The greater MHC differentiation among populations was negatively correlated with similarity in blood parasites (prevalence and diversity of parasite strains) between populations. Even at low prevalence and small geographical scale, haemosporidian parasites might contribute to structure the variability of immune genes among populations of hosts.
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Affiliation(s)
- Coraline Bichet
- Biogéosciences, UMR CNRS 6282, Université de Bourgogne 6 Boulevard Gabriel, 21000, Dijon, France ; Laboratoire LBBE, UMR CNRS 5558, Université Claude Bernard Lyon 1 bâtiment Mendel, 43 boulevard du 11 novembre 1918, 69622, Villeurbanne Cedex, France
| | - Yoshan Moodley
- Department of Zoology, University of Venda Private Bag X5050, Thohoyandou, 0950, South Africa ; Department of Integrative Biology and Evolution, Konrad-Lorenz-Institute of Ethology, University of Veterinarian Medicine Vienna Savoyenstr. 1a, A-1160, Vienna, Austria
| | - Dustin J Penn
- Department of Integrative Biology and Evolution, Konrad-Lorenz-Institute of Ethology, University of Veterinarian Medicine Vienna Savoyenstr. 1a, A-1160, Vienna, Austria
| | - Gabriele Sorci
- Biogéosciences, UMR CNRS 6282, Université de Bourgogne 6 Boulevard Gabriel, 21000, Dijon, France
| | - Stéphane Garnier
- Biogéosciences, UMR CNRS 6282, Université de Bourgogne 6 Boulevard Gabriel, 21000, Dijon, France
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Larson WA, Seeb JE, Dann TH, Schindler DE, Seeb LW. Signals of heterogeneous selection at an MHC locus in geographically proximate ecotypes of sockeye salmon. Mol Ecol 2014; 23:5448-61. [DOI: 10.1111/mec.12949] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 09/26/2014] [Accepted: 09/29/2014] [Indexed: 11/29/2022]
Affiliation(s)
- Wesley A. Larson
- School of Aquatic and Fishery Sciences; University of Washington; 1122 NE Boat Street Box 355020 Seattle WA 98195-5020 USA
| | - James E. Seeb
- School of Aquatic and Fishery Sciences; University of Washington; 1122 NE Boat Street Box 355020 Seattle WA 98195-5020 USA
| | - Tyler H. Dann
- School of Aquatic and Fishery Sciences; University of Washington; 1122 NE Boat Street Box 355020 Seattle WA 98195-5020 USA
- Gene Conservation Laboratory; Alaska Department of Fish and Game; 333 Raspberry Road Anchorage AK 99518 USA
| | - Daniel E. Schindler
- School of Aquatic and Fishery Sciences; University of Washington; 1122 NE Boat Street Box 355020 Seattle WA 98195-5020 USA
| | - Lisa W. Seeb
- School of Aquatic and Fishery Sciences; University of Washington; 1122 NE Boat Street Box 355020 Seattle WA 98195-5020 USA
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28
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Lemay MA, Russello MA. Diversity and relative abundance of the bacterial pathogen, Flavobacterium spp., infecting reproductive ecotypes of kokanee salmon. BMC Res Notes 2014; 7:778. [PMID: 25367228 PMCID: PMC4228061 DOI: 10.1186/1756-0500-7-778] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 10/24/2014] [Indexed: 11/28/2022] Open
Abstract
Background Understanding the distribution and abundance of pathogens can provide insight into the evolution and ecology of their host species. Previous research in kokanee, the freshwater form of sockeye salmon (Oncorhynchus nerka), found evidence that populations spawning in streams may experience a greater pathogen load compared with populations that spawn on beaches. In this study we tested for differences in the abundance and diversity of the gram-negative bacteria, Flavobacterium spp., infecting tissues of kokanee in both of these spawning habitats (streams and beaches). Molecular assays were carried out using primers designed to amplify a ~200 nucleotide region of the gene encoding the ATP synthase alpha subunit (AtpA) within the genus Flavobacterium. Using a combination of DNA sequencing and quantitative PCR (qPCR) we compared the diversity and relative abundance of Flavobacterium AtpA amplicons present in DNA extracted from tissue samples of kokanee collected from each spawning habitat. Results We identified 10 Flavobacterium AtpA haplotypes among the tissues of stream-spawning kokanee and seven haplotypes among the tissues of beach-spawning kokanee, with only two haplotypes shared between spawning habitats. Haplotypes occurring in the same clade as F. psychrophilum were the most prevalent (92% of all reads, 60% of all haplotypes), and occurred in kokanee from both spawning habitats (streams and beaches). Subsequent qPCR assays did not find any significant difference in the relative abundance of Flavobacterium AtpA amplicons between samples from the different spawning habitats. Conclusions We confirmed the presence of Flavobacterium spp. in both spawning habitats and found weak evidence for increased Flavobacterium diversity in kokanee sampled from stream-spawning sites. However, the quantity of Flavobacterium DNA did not differ between spawning habitats. We recommend further study aimed at quantifying pathogen diversity and abundance in population-level samples of kokanee combined with environmental sampling to better understand the ecology of pathogen infection in this species. Electronic supplementary material The online version of this article (doi:10.1186/1756-0500-7-778) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Matthew A Lemay
- University of British Columbia, Okanagan Campus, 3247 University Way, Kelowna, BC V1V 1V7, Canada.
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Herdegen M, Babik W, Radwan J. Selective pressures on MHC class II genes in the guppy (Poecilia reticulata) as inferred by hierarchical analysis of population structure. J Evol Biol 2014; 27:2347-59. [PMID: 25244157 DOI: 10.1111/jeb.12476] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Revised: 08/08/2014] [Accepted: 08/11/2014] [Indexed: 11/29/2022]
Abstract
Genes of the major histocompatibility complex, which are the most polymorphic of all vertebrate genes, are a pre-eminent system for the study of selective pressures that arise from host-pathogen interactions. Balancing selection capable of maintaining high polymorphism should lead to the homogenization of MHC allele frequencies among populations, but there is some evidence to suggest that diversifying selection also operates on the MHC. However, the pattern of population structure observed at MHC loci is likely to depend on the spatial and/or temporal scale examined. Here, we investigated selection acting on MHC genes at different geographic scales using Venezuelan guppy populations inhabiting four regions. We found a significant correlation between MHC and microsatellite allelic richness across populations, which suggests the role of genetic drift in shaping MHC diversity. However, compared to microsatellites, more MHC variation was explained by differences between populations within larger geographic regions and less by the differences between the regions. Furthermore, among proximate populations, variation in MHC allele frequencies was significantly higher compared to microsatellites, indicating that selection acting on MHC may increase population structure at small spatial scales. However, in populations that have significantly diverged at neutral markers, the population-genetic signature of diversifying selection may be eradicated in the long term by that of balancing selection, which acts to preserve rare alleles and thus maintain a common pool of MHC alleles.
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Affiliation(s)
- M Herdegen
- Institute of Environmental Sciences, Jagiellonian University, Kraków, Poland
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Miller KM, Teffer A, Tucker S, Li S, Schulze AD, Trudel M, Juanes F, Tabata A, Kaukinen KH, Ginther NG, Ming TJ, Cooke SJ, Hipfner JM, Patterson DA, Hinch SG. Infectious disease, shifting climates, and opportunistic predators: cumulative factors potentially impacting wild salmon declines. Evol Appl 2014; 7:812-55. [PMID: 25469162 PMCID: PMC4227861 DOI: 10.1111/eva.12164] [Citation(s) in RCA: 151] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Accepted: 03/06/2014] [Indexed: 12/23/2022] Open
Abstract
Emerging diseases are impacting animals under high-density culture, yet few studies assess their importance to wild populations. Microparasites selected for enhanced virulence in culture settings should be less successful maintaining infectivity in wild populations, as once the host dies, there are limited opportunities to infect new individuals. Instead, moderately virulent microparasites persisting for long periods across multiple environments are of greatest concern. Evolved resistance to endemic microparasites may reduce susceptibilities, but as barriers to microparasite distributions are weakened, and environments become more stressful, unexposed populations may be impacted and pathogenicity enhanced. We provide an overview of the evolutionary and ecological impacts of infectious diseases in wild salmon and suggest ways in which modern technologies can elucidate the microparasites of greatest potential import. We present four case studies that resolve microparasite impacts on adult salmon migration success, impact of river warming on microparasite replication, and infection status on susceptibility to predation. Future health of wild salmon must be considered in a holistic context that includes the cumulative or synergistic impacts of multiple stressors. These approaches will identify populations at greatest risk, critically needed to manage and potentially ameliorate the shifts in current or future trajectories of wild populations.
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Affiliation(s)
- Kristina M Miller
- Pacific Biological Station, Fisheries and Oceans CanadaNanaimo, BC, Canada
- Forest and Conservation Sciences, University of British ColumbiaVancouver, BC, Canada
| | - Amy Teffer
- Biology Department, University of VictoriaVictoria, BC, Canada
| | - Strahan Tucker
- Pacific Biological Station, Fisheries and Oceans CanadaNanaimo, BC, Canada
| | - Shaorong Li
- Pacific Biological Station, Fisheries and Oceans CanadaNanaimo, BC, Canada
| | - Angela D Schulze
- Pacific Biological Station, Fisheries and Oceans CanadaNanaimo, BC, Canada
| | - Marc Trudel
- Pacific Biological Station, Fisheries and Oceans CanadaNanaimo, BC, Canada
- Biology Department, University of VictoriaVictoria, BC, Canada
| | - Francis Juanes
- Biology Department, University of VictoriaVictoria, BC, Canada
| | - Amy Tabata
- Pacific Biological Station, Fisheries and Oceans CanadaNanaimo, BC, Canada
| | - Karia H Kaukinen
- Pacific Biological Station, Fisheries and Oceans CanadaNanaimo, BC, Canada
| | - Norma G Ginther
- Pacific Biological Station, Fisheries and Oceans CanadaNanaimo, BC, Canada
| | - Tobi J Ming
- Pacific Biological Station, Fisheries and Oceans CanadaNanaimo, BC, Canada
| | - Steven J Cooke
- Fish Ecology and Conservation Physiology Laboratory, Department of Biology, Carleton UniverisyOttawa, ON, Canada
| | - J Mark Hipfner
- Environment Canada, Wildlife Research DivisionDelta, BC, Canada
| | - David A Patterson
- Fisheries and Oceans Canada, School of Resource and Environmental Management, Simon Fraser University, Science BranchBurnaby, BC, Canada
| | - Scott G Hinch
- Forest and Conservation Sciences, University of British ColumbiaVancouver, BC, Canada
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Yao YF, Dai QX, Li J, Ni QY, Zhang MW, Xu HL. Genetic diversity and differentiation of the rhesus macaque (Macaca mulatta) population in western Sichuan, China, based on the second exon of the major histocompatibility complex class II DQB (MhcMamu-DQB1) alleles. BMC Evol Biol 2014; 14:130. [PMID: 24930092 PMCID: PMC4070090 DOI: 10.1186/1471-2148-14-130] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2013] [Accepted: 06/02/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Rhesus macaques living in western Sichuan, China, have been separated into several isolated populations due to habitat fragmentation. Previous studies based on the neutral or nearly neutral markers (mitochondrial DNA or microsatellites) showed high levels of genetic diversity and moderate genetic differentiation in the Sichuan rhesus macaques. Variation at the major histocompatibility complex (MHC) loci is widely accepted as being maintained by balancing selection, even with a low level of neutral variability in some species. However, in small and isolated or bottlenecked populations, balancing selection may be overwhelmed by genetic drift. To estimate microevolutionary forces acting on the isolated rhesus macaque populations, we examined genetic variation at Mhc-DQB1 loci in 119 wild rhesus macaques from five geographically isolated populations in western Sichuan, China, and compared the levels of MHC variation and differentiation among populations with that previously observed at neutral microsatellite markers. RESULTS 23 Mamu-DQB1 alleles were identified in 119 rhesus macaques in western Sichuan, China. These macaques exhibited relatively high levels of genetic diversity at Mamu-DQB1. The Hanyuan population presented the highest genetic variation, whereas the Heishui population was the lowest. Analysis of molecular variance (AMOVA) and pairwise FST values showed moderate genetic differentiation occurring among the five populations at the Mhc-DQB1 locus. Non-synonymous substitutions occurred at a higher frequency than synonymous substitutions in the peptide binding region. Levels of MHC variation within rhesus macaque populations are concordant with microsatellite variation. On the phylogenetic tree for the rhesus and crab-eating macaques, extensive allele or allelic lineage sharing is observed between the two species. CONCLUSIONS Phylogenetic analyses confirm the apparent trans-species model of evolution of the Mhc-DQB1 genes in these macaques. Balancing selection plays an important role in sharing allelic lineages between species, but genetic drift may share balancing selection dominance to maintain MHC diversity. Great divergence at neutral or adaptive markers showed that moderate genetic differentiation had occurred in rhesus macaque populations in western Sichuan, China, due to the habitat fragmentation caused by long-term geographic barriers and human activity. The Heishui population should be paid more attention for its lowest level of genetic diversity and relatively great divergence from others.
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Affiliation(s)
- Yong-Fang Yao
- College of Animal Science and Technology, Sichuan Agricultural University, Ya´an 625014, China
| | - Qiu-Xia Dai
- College of Animal Science and Technology, Sichuan Agricultural University, Ya´an 625014, China
| | - Jing Li
- College of Life Sciences, Sichuan University, Chengdu 610064, China
| | - Qing-Yong Ni
- College of Animal Science and Technology, Sichuan Agricultural University, Ya´an 625014, China
| | - Ming-Wang Zhang
- College of Animal Science and Technology, Sichuan Agricultural University, Ya´an 625014, China
| | - Huai-Liang Xu
- College of Animal Science and Technology, Sichuan Agricultural University, Ya´an 625014, China
- Experimental Animal Engineering Center/National Experimental Macaque Reproduce Laboratory, Sichuan Agricultural Universiy, Ya′an 625014, China
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Tobler M, Plath M, Riesch R, Schlupp I, Grasse A, Munimanda GK, Setzer C, Penn DJ, Moodley Y. Selection from parasites favours immunogenetic diversity but not divergence among locally adapted host populations. J Evol Biol 2014; 27:960-74. [PMID: 24725091 DOI: 10.1111/jeb.12370] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Accepted: 03/09/2014] [Indexed: 11/26/2022]
Abstract
The unprecedented polymorphism in the major histocompatibility complex (MHC) genes is thought to be maintained by balancing selection from parasites. However, do parasites also drive divergence at MHC loci between host populations, or do the effects of balancing selection maintain similarities among populations? We examined MHC variation in populations of the livebearing fish Poecilia mexicana and characterized their parasite communities. Poecilia mexicana populations in the Cueva del Azufre system are locally adapted to darkness and the presence of toxic hydrogen sulphide, representing highly divergent ecotypes or incipient species. Parasite communities differed significantly across populations, and populations with higher parasite loads had higher levels of diversity at class II MHC genes. However, despite different parasite communities, marked divergence in adaptive traits and in neutral genetic markers, we found MHC alleles to be remarkably similar among host populations. Our findings indicate that balancing selection from parasites maintains immunogenetic diversity of hosts, but this process does not promote MHC divergence in this system. On the contrary, we suggest that balancing selection on immunogenetic loci may outweigh divergent selection causing divergence, thereby hindering host divergence and speciation. Our findings support the hypothesis that balancing selection maintains MHC similarities among lineages during and after speciation (trans-species evolution).
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Affiliation(s)
- M Tobler
- Department of Zoology, Oklahoma State University, Stillwater, OK, USA
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Froeschke G, von der Heyden S. A review of molecular approaches for investigating patterns of coevolution in marine host-parasite relationships. Adv Parasitol 2014; 84:209-52. [PMID: 24480315 DOI: 10.1016/B978-0-12-800099-1.00004-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Parasites and their relationships with hosts play a crucial role in the evolutionary pathways of every living organism. One method of investigating host-parasite systems is using a molecular approach. This is particularly important as analyses based solely on morphology or laboratory studies of parasites and their hosts do not take into account historical evolutionary interactions that can shape the distribution, abundance and population structure of parasites and their hosts. However, the predominant host-parasite coevolution literature has focused on terrestrial hosts and their parasites, and there still is a lack of studies in marine environments. Given that marine systems are generally more open than terrestrial ones, they provide fascinating opportunities for large-scale (as well as small-scale) geographic studies. Further, patterns and processes of genetic structuring and systematics are becoming more available across many different taxa (but especially fishes) in many marine systems, providing an excellent basis for examining whether parasites follow host population/species structure. In this chapter, we first highlight the factors and processes that challenge our ability to interpret evolutionary patterns of coevolution of hosts and their parasites in marine systems at different spatial, temporal and taxonomic scales. We then review the use of the most commonly utilized genetic markers in studying marine host-parasite systems. We give an overview and discuss which molecular methodologies resolve evolutionary relationships best and also discuss the applicability of new approaches, such as next-generation sequencing and studies utilizing functional markers to gain insights into more contemporary processes shaping host-parasite relationships.
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McClelland EK, Ming TJ, Tabata A, Kaukinen KH, Beacham TD, Withler RE, Miller KM. Patterns of selection and allele diversity of class I and class II major histocompatibility loci across the species range of sockeye salmon (Oncorhynchus nerka). Mol Ecol 2013; 22:4783-800. [DOI: 10.1111/mec.12424] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2013] [Revised: 06/14/2013] [Accepted: 06/17/2013] [Indexed: 11/29/2022]
Affiliation(s)
- Erin K. McClelland
- Fisheries and Oceans Canada; Pacific Biological Station 3190 Hammond Bay Rd Nanaimo BC V9T 6N7 Canada
| | - Tobi J. Ming
- Fisheries and Oceans Canada; Pacific Biological Station 3190 Hammond Bay Rd Nanaimo BC V9T 6N7 Canada
| | - Amy Tabata
- Fisheries and Oceans Canada; Pacific Biological Station 3190 Hammond Bay Rd Nanaimo BC V9T 6N7 Canada
| | - Karia H. Kaukinen
- Fisheries and Oceans Canada; Pacific Biological Station 3190 Hammond Bay Rd Nanaimo BC V9T 6N7 Canada
| | - Terry D. Beacham
- Fisheries and Oceans Canada; Pacific Biological Station 3190 Hammond Bay Rd Nanaimo BC V9T 6N7 Canada
| | - Ruth E. Withler
- Fisheries and Oceans Canada; Pacific Biological Station 3190 Hammond Bay Rd Nanaimo BC V9T 6N7 Canada
| | - Kristina M. Miller
- Fisheries and Oceans Canada; Pacific Biological Station 3190 Hammond Bay Rd Nanaimo BC V9T 6N7 Canada
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Zhang M, He H. Parasite-mediated selection of major histocompatibility complex variability in wild brandt's voles (Lasiopodomys brandtii) from Inner Mongolia, China. BMC Evol Biol 2013; 13:149. [PMID: 23848494 PMCID: PMC3720540 DOI: 10.1186/1471-2148-13-149] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Accepted: 06/27/2013] [Indexed: 11/21/2022] Open
Abstract
Background Genes of the major histocompatibility complex (MHC) exhibit high levels of variability, which is believed to have arisen through pathogen-mediated selection. We investigated the relationship between parasite load and genetic diversity at selectively neutral, non-coding markers (microsatellites) and adaptive genetic variation at a functionally important part of the MHC in six independent natural populations of Brandt’s voles (Lasiopodomys brandtii) from two regions of the Xilingol Grassland area of Inner Mongolia. Results Two-hundred and fifty-two voles were screened for gastrointestinal parasites, and were assessed for genetic variation. Parasite screening was done through non-invasive fecal egg counts, while allelic diversity was determined via single-stranded conformation polymorphism and DNA sequencing. We detected eight distinct helminth egg morphotypes. A total of 10 microsatellite loci were genotyped and 19 unique MHC class II B alleles were isolated. The rate of nonsynonymous substitutions (dN) exceeded the rate of synonymous substitutions (dS) at putative antigen binding sites of DRB. Neutral and adaptive genetic diversity differed between the six vole populations. To test the main pathogen-driven selection hypotheses for the maintenance of host MHC diversity and parasite species-specific co-evolutionary effects, multivariate approaches (generalized linear mixed models) were used to test for associations between the MHC class II DRB genotype and infections with nematodes. We found no evidence for heterozygote advantage, and overall heterozygosity was lower than expected in the MHC alleles. We identified an association between the parasite load and specific MHC alleles in the voles, and this pattern varied between geographic regions. Conclusions The results suggest that MHC variability in Brandt’s voles is maintained by rare allele advantage and fluctuating selection, but the data failed to show any heterozygote advantage effect. Our results add to a growing body of evidence showing that the mode and relative strength of pathogen-driven selection acting on MHC diversity varies within specific wild populations. In addition, our study contributes to the understanding of what maintains MHC diversity, of host-pathogen coevolution and of how genetic diversity is maintained in voles.
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Affiliation(s)
- Min Zhang
- Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
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Pavey SA, Sevellec M, Adam W, Normandeau E, Lamaze FC, Gagnaire PA, Filteau M, Hebert FO, Maaroufi H, Bernatchez L. Nonparallelism in MHCIIβ diversity accompanies nonparallelism in pathogen infection of lake whitefish (Coregonus clupeaformis) species pairs as revealed by next-generation sequencing. Mol Ecol 2013; 22:3833-49. [DOI: 10.1111/mec.12358] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Revised: 04/03/2013] [Accepted: 04/08/2013] [Indexed: 11/26/2022]
Affiliation(s)
- Scott A. Pavey
- Departement de Biologie; Institut de Biologie Intégrative et des Systèmes (IBIS); Université Laval; Pavillon Charles-Eugene-Marchand Québec Québec Canada G1V 0A6
| | - Maelle Sevellec
- Departement de Biologie; Institut de Biologie Intégrative et des Systèmes (IBIS); Université Laval; Pavillon Charles-Eugene-Marchand Québec Québec Canada G1V 0A6
| | - William Adam
- Departement de Biologie; Institut de Biologie Intégrative et des Systèmes (IBIS); Université Laval; Pavillon Charles-Eugene-Marchand Québec Québec Canada G1V 0A6
| | - Eric Normandeau
- Departement de Biologie; Institut de Biologie Intégrative et des Systèmes (IBIS); Université Laval; Pavillon Charles-Eugene-Marchand Québec Québec Canada G1V 0A6
| | - Fabien C. Lamaze
- Departement de Biologie; Institut de Biologie Intégrative et des Systèmes (IBIS); Université Laval; Pavillon Charles-Eugene-Marchand Québec Québec Canada G1V 0A6
| | - Pierre-Alexandre Gagnaire
- Departement de Biologie; Institut de Biologie Intégrative et des Systèmes (IBIS); Université Laval; Pavillon Charles-Eugene-Marchand Québec Québec Canada G1V 0A6
- Institut des Sciences de l'Evolution - Montpellier (ISEM); Universite Montpellier II; Place Eugene Bataillon 34095 Montpellier Cedex France
| | - Marie Filteau
- Departement de Biologie; Institut de Biologie Intégrative et des Systèmes (IBIS); Université Laval; Pavillon Charles-Eugene-Marchand Québec Québec Canada G1V 0A6
| | - Francois Olivier Hebert
- Departement de Biologie; Institut de Biologie Intégrative et des Systèmes (IBIS); Université Laval; Pavillon Charles-Eugene-Marchand Québec Québec Canada G1V 0A6
| | - Halim Maaroufi
- Departement de Biologie; Institut de Biologie Intégrative et des Systèmes (IBIS); Université Laval; Pavillon Charles-Eugene-Marchand Québec Québec Canada G1V 0A6
- Plate-forme de Bio-informatique and Institut de Biologie Intégrative et des Systèmes; Université Laval; Pavillon Charles-Eugene-Marchand Québec Québec Canada G1V 0A6
| | - Louis Bernatchez
- Departement de Biologie; Institut de Biologie Intégrative et des Systèmes (IBIS); Université Laval; Pavillon Charles-Eugene-Marchand Québec Québec Canada G1V 0A6
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O'Farrell B, Benzie JA, McGinnity P, de Eyto E, Dillane E, Coughlan J, Cross TF. Selection and phylogenetics of salmonid MHC class I: wild brown trout (Salmo trutta) differ from a non-native introduced strain. PLoS One 2013; 8:e63035. [PMID: 23667568 DOI: 10.1371/journal.pone.0063035] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Accepted: 03/29/2013] [Indexed: 01/29/2023] Open
Abstract
We tested how variation at a gene of adaptive importance, MHC class I (UBA), in a wild, endemic Salmo trutta population compared to that in both a previously studied non-native S. trutta population and a co-habiting Salmo salar population (a sister species). High allelic diversity is observed and allelic divergence is much higher than that noted previously for co-habiting S. salar. Recombination was found to be important to population-level divergence. The α1 and α2 domains of UBA demonstrate ancient lineages but novel lineages are also identified at both domains in this work. We also find examples of recombination between UBA and the non-classical locus, ULA. Evidence for strong diversifying selection was found at a discrete suite of S. trutta UBA amino acid sites. The pattern was found to contrast with that found in re-analysed UBA data from an artificially stocked S. trutta population.
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Kamath PL, Getz WM. Unraveling the effects of selection and demography on immune gene variation in free-ranging plains zebra (Equus quagga) populations. PLoS One 2012; 7:e50971. [PMID: 23251409 PMCID: PMC3522668 DOI: 10.1371/journal.pone.0050971] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Accepted: 10/29/2012] [Indexed: 11/18/2022] Open
Abstract
Demography, migration and natural selection are predominant processes affecting the distribution of genetic variation among natural populations. Many studies use neutral genetic markers to make inferences about population history. However, the investigation of functional coding loci, which directly reflect fitness, is critical to our understanding of species' ecology and evolution. Immune genes, such as those of the Major Histocompatibility Complex (MHC), play an important role in pathogen recognition and provide a potent model system for studying selection. We contrasted diversity patterns of neutral data with MHC loci, ELA-DRA and -DQA, in two southern African plains zebra (Equus quagga) populations: Etosha National Park, Namibia, and Kruger National Park, South Africa. Results from neutrality tests, along with observations of elevated diversity and low differentiation across populations, supported previous genus-level evidence for balancing selection at these loci. Despite being low, MHC divergence across populations was significant and may be attributed to drift effects typical of geographically separated populations experiencing little to no gene flow, or alternatively to shifting allele frequency distributions driven by spatially variable and fluctuating pathogen communities. At the DRA, zebra exhibited geographic differentiation concordant with microsatellites and reduced levels of diversity in Etosha due to highly skewed allele frequencies that could not be explained by demography, suggestive of spatially heterogeneous selection and local adaptation. This study highlights the complexity in which selection affects immune gene diversity and warrants the need for further research on the ecological mechanisms shaping patterns of adaptive variation among natural populations.
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Affiliation(s)
- Pauline L Kamath
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, United States of America.
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Luo MF, Pan HJ, Liu ZJ, Li M. Balancing selection and genetic drift at major histocompatibility complex class II genes in isolated populations of golden snub-nosed monkey (Rhinopithecus roxellana). BMC Evol Biol 2012; 12:207. [PMID: 23083308 PMCID: PMC3532231 DOI: 10.1186/1471-2148-12-207] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2012] [Accepted: 10/05/2012] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND Small, isolated populations often experience loss of genetic variation due to random genetic drift. Unlike neutral or nearly neutral markers (such as mitochondrial genes or microsatellites), major histocompatibility complex (MHC) genes in these populations may retain high levels of polymorphism due to balancing selection. The relative roles of balancing selection and genetic drift in either small isolated or bottlenecked populations remain controversial. In this study, we examined the mechanisms maintaining polymorphisms of MHC genes in small isolated populations of the endangered golden snub-nosed monkey (Rhinopithecus roxellana) by comparing genetic variation found in MHC and microsatellite loci. There are few studies of this kind conducted on highly endangered primate species. RESULTS Two MHC genes were sequenced and sixteen microsatellite loci were genotyped from samples representing three isolated populations. We isolated nine DQA1 alleles and sixteen DQB1 alleles and validated expression of the alleles. Lowest genetic variation for both MHC and microsatellites was found in the Shennongjia (SNJ) population. Historical balancing selection was revealed at both the DQA1 and DQB1 loci, as revealed by excess non-synonymous substitutions at antigen binding sites (ABS) and maximum-likelihood-based random-site models. Patterns of microsatellite variation revealed population structure. FST outlier analysis showed that population differentiation at the two MHC loci was similar to the microsatellite loci. CONCLUSIONS MHC genes and microsatellite loci showed the same allelic richness pattern with the lowest genetic variation occurring in SNJ, suggesting that genetic drift played a prominent role in these isolated populations. As MHC genes are subject to selective pressures, the maintenance of genetic variation is of particular interest in small, long-isolated populations. The results of this study may contribute to captive breeding and translocation programs for endangered species.
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Affiliation(s)
- Mao-Fang Luo
- Key laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, 1-5 Beixhenxi Road, Chaoyang, Beijing, 100101, China
- Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
- Graduate School of the Chinese Academy of Sciences, Beijing, 100049, China
| | - Hui-Juan Pan
- College of Nature Conservation, Beijing Forestry University, Beijing, 100083, China
| | - Zhi-Jin Liu
- Key laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, 1-5 Beixhenxi Road, Chaoyang, Beijing, 100101, China
| | - Ming Li
- Key laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, 1-5 Beixhenxi Road, Chaoyang, Beijing, 100101, China
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Abstract
Allorecognition is the ability of an organism to differentiate self or close relatives from unrelated individuals. The best known applications of allorecognition are the prevention of inbreeding in hermaphroditic species (e.g., the self-incompatibility [SI] systems in plants), the vertebrate immune response to foreign antigens mediated by MHC loci, and somatic fusion, where two genetically independent individuals physically join to become a chimera. In the few model systems where the loci governing allorecognition outcomes have been identified, the corresponding proteins have exhibited exceptional polymorphism. But information about the evolution of this polymorphism outside MHC is limited. We address this subject in the ascidian Botryllus schlosseri, where allorecognition outcomes are determined by a single locus, called FuHC (Fusion/HistoCompatibility). Molecular variation in FuHC is distributed almost entirely within populations, with very little evidence for differentiation among different populations. Mutation plays a larger role than recombination in the creation of FuHC polymorphism. A selection statistic, neutrality tests, and distribution of variation within and among different populations all provide evidence for selection acting on FuHC, but are not in agreement as to whether the selection is balancing or directional.
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Affiliation(s)
- Marie L Nydam
- Division of Science and Mathematics, Centre College, Danville, Kentucky 40422, USA.
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Ackerman MW, Templin WD, Seeb JE, Seeb LW. Landscape heterogeneity and local adaptation define the spatial genetic structure of Pacific salmon in a pristine environment. CONSERV GENET 2012. [DOI: 10.1007/s10592-012-0401-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Limborg MT, Blankenship SM, Young SF, Utter FM, Seeb LW, Hansen MHH, Seeb JE. Signatures of natural selection among lineages and habitats in Oncorhynchus mykiss. Ecol Evol 2012; 2:1-18. [PMID: 22408722 PMCID: PMC3297173 DOI: 10.1002/ece3.59] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Revised: 09/27/2011] [Accepted: 09/27/2011] [Indexed: 12/21/2022] Open
Abstract
Recent advances in molecular interrogation techniques now allow unprecedented genomic inference about the role of adaptive genetic divergence in wild populations. We used high-throughput genotyping to screen a genome-wide panel of 276 single nucleotide polymorphisms (SNPs) for the economically and culturally important salmonid Oncorhynchus mykiss. Samples included 805 individuals from 11 anadromous and resident populations from the northwestern United States and British Columbia, and represented two major lineages including paired populations of each life history within single drainages of each lineage. Overall patterns of variation affirmed clear distinctions between lineages and in most instances, isolation by distance within them. Evidence for divergent selection at eight candidate loci included significant landscape correlations, particularly with temperature. High diversity of two nonsynonymous mutations within the peptide-binding region of the major histocompatibility complex (MHC) class II (DAB) gene provided signatures of balancing selection. Weak signals for potential selection between sympatric resident and anadromous populations were revealed from genome scans and allele frequency comparisons. Our results suggest an important adaptive role for immune-related functions and present a large genomic resource for future studies
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Lillie M, Woodward RE, Sanderson CE, Eldridge MDB, Belov K. Diversity at the major histocompatibility complex Class II in the platypus, Ornithorhynchus anatinus. J Hered 2012; 103:467-78. [PMID: 22563128 DOI: 10.1093/jhered/ess012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The platypus (Ornithorhynchus anatinus) is the sole survivor of a previously widely distributed and diverse lineage of ornithorhynchid monotremes. Its dependence on healthy water systems imposes an inherent sensitivity to habitat degradation and climate change. Here, we compare genetic diversity at the major histocompatibility complex (MHC) Class II-DZB gene and 3 MHC-associated microsatellite markers with diversity at 6 neutral microsatellite markers in 70 platypuses from across their range, including the mainland of Australia and the isolated populations of Tasmania, King Island, and Kangaroo Island. Overall, high DZB diversity was observed in the platypus, with 57 DZB β1 alleles characterized. Significant positive selection was detected within the DZB peptide-binding region, promoting variation in this domain. Low levels of genetic diversity were detected at all markers in the 2 island populations, King Island (endemic) and Kangaroo Island (introduced), with the King Island platypuses monomorphic at the DZB locus. Loss of MHC diversity on King Island is of concern, as the population may have compromised immunological fitness and reduced ability to resist changing environmental conditions.
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Affiliation(s)
- Mette Lillie
- Faculty of Veterinary Science, University of Sydney, Sydney, NSW 2006, Australia
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Marsden CD, Woodroffe R, Mills MGL, McNutt JW, Creel S, Groom R, Emmanuel M, Cleaveland S, Kat P, Rasmussen GSA, Ginsberg J, Lines R, André JM, Begg C, Wayne RK, Mable BK. Spatial and temporal patterns of neutral and adaptive genetic variation in the endangered African wild dog (Lycaon pictus). Mol Ecol 2012; 21:1379-93. [PMID: 22320891 DOI: 10.1111/j.1365-294x.2012.05477.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Deciphering patterns of genetic variation within a species is essential for understanding population structure, local adaptation and differences in diversity between populations. Whilst neutrally evolving genetic markers can be used to elucidate demographic processes and genetic structure, they are not subject to selection and therefore are not informative about patterns of adaptive variation. As such, assessments of pertinent adaptive loci, such as the immunity genes of the major histocompatibility complex (MHC), are increasingly being incorporated into genetic studies. In this study, we combined neutral (microsatellite, mtDNA) and adaptive (MHC class II DLA-DRB1 locus) markers to elucidate the factors influencing patterns of genetic variation in the African wild dog (Lycaon pictus); an endangered canid that has suffered extensive declines in distribution and abundance. Our genetic analyses found all extant wild dog populations to be relatively small (N(e) < 30). Furthermore, through coalescent modelling, we detected a genetic signature of a recent and substantial demographic decline, which correlates with human expansion, but contrasts with findings in some other African mammals. We found strong structuring of wild dog populations, indicating the negative influence of extensive habitat fragmentation and loss of gene flow between habitat patches. Across populations, we found that the spatial and temporal structure of microsatellite diversity and MHC diversity were correlated and strongly influenced by demographic stability and population size, indicating the effects of genetic drift in these small populations. Despite this correlation, we detected signatures of selection at the MHC, implying that selection has not been completely overwhelmed by genetic drift.
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Affiliation(s)
- Clare D Marsden
- Institute of Biodiversity, Animal Health & Comparative Medicine, University of Glasgow, Glasgow, UK.
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Hawley DM, Fleischer RC. Contrasting epidemic histories reveal pathogen-mediated balancing selection on class II MHC diversity in a wild songbird. PLoS One 2012; 7:e30222. [PMID: 22291920 PMCID: PMC3264569 DOI: 10.1371/journal.pone.0030222] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Accepted: 12/14/2011] [Indexed: 11/20/2022] Open
Abstract
The extent to which pathogens maintain the extraordinary polymorphism at vertebrate Major Histocompatibility Complex (MHC) genes via balancing selection has intrigued evolutionary biologists for over half a century, but direct tests remain challenging. Here we examine whether a well-characterized epidemic of Mycoplasmal conjunctivitis resulted in balancing selection on class II MHC in a wild songbird host, the house finch (Carpodacus mexicanus). First, we confirmed the potential for pathogen-mediated balancing selection by experimentally demonstrating that house finches with intermediate to high multi-locus MHC diversity are more resistant to challenge with Mycoplasma gallisepticum. Second, we documented sequence and diversity-based signatures of pathogen-mediated balancing selection at class II MHC in exposed host populations that were absent in unexposed, control populations across an equivalent time period. Multi-locus MHC diversity significantly increased in exposed host populations following the epidemic despite initial compromised diversity levels from a recent introduction bottleneck in the exposed host range. We did not observe equivalent changes in allelic diversity or heterozygosity across eight neutral microsatellite loci, suggesting that the observations reflect selection rather than neutral demographic processes. Our results indicate that a virulent pathogen can exert sufficient balancing selection on class II MHC to rescue compromised levels of genetic variation for host resistance in a recently bottlenecked population. These results provide evidence for Haldane's long-standing hypothesis that pathogens directly contribute to the maintenance of the tremendous levels of genetic variation detected in natural populations of vertebrates.
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Affiliation(s)
- Dana M Hawley
- Center for Conservation and Evolutionary Genetics, Smithsonian Institution, Washington DC, United States of America.
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Girard P, Angers B. The functional gene diversity in natural populations over postglacial areas: the shaping mechanisms behind genetic composition of longnose dace (Rhinichthys cataractae) in northeastern North America. J Mol Evol 2011; 73:45-57. [PMID: 21861120 DOI: 10.1007/s00239-011-9456-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2011] [Accepted: 08/09/2011] [Indexed: 10/17/2022]
Abstract
The diversity of functional genes and the related processes are important issues for conservation biology. This is especially relevant for populations that have suffered from demographic reduction as a consequence of the processes of postglacial colonization. In this perspective, the aims of the present study are (1) to quantify the genetic diversity of functional genes and (2) to disentangle the long- and short-term effects of natural selection that shapes genetic diversity from those of drift, mutation, and allopatric fragmentation. This research was conducted using an extensive genetic polymorphism analysis of populations of longnose dace (Rhinichthys cataractae) living over an area once covered by Pleistocene glaciations. The sequence and diversity of one exon of three genes (MHC IIβ, growth hormone, and trypsin) were jointly analyzed with non-coding nuclear loci from 27 populations; these populations were sampled over four major basins of northeastern North America. The survey revealed a surprisingly low allelic richness, especially for the MHC gene, considering the number of individuals and populations sampled. The results suggest that there is a complex mixture of different evolutionary processes shaping the level of polymorphism among longnose dace. While our study underlines the importance of the short-term effects of neutral processes and the major impact of post-glacial colonization on gene diversity, locally dependent balancing selection was detected on MHC. From this perspective, our results support an understanding of the importance of drift on functional gene diversity but also highlight the transient effects of natural selection on allelic composition, even in populations that show drastic reduction of genetic diversity.
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Affiliation(s)
- Philippe Girard
- Département de Géographie, Université de Montréal, C.P. 6128, Succ. Centre-Ville, Montréal, QC H3C 3J7, Canada.
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Campos JL, Bellocq JGD, Schaschl H, Suchentrunk F. MHC class II DQA gene variation across cohorts of brown hares (Lepus europaeus) from eastern Austria: Testing for different selection hypotheses. Mamm Biol 2011. [DOI: 10.1016/j.mambio.2010.05.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Gomez-Uchida D, Seeb JE, Smith MJ, Habicht C, Quinn TP, Seeb LW. Single nucleotide polymorphisms unravel hierarchical divergence and signatures of selection among Alaskan sockeye salmon (Oncorhynchus nerka) populations. BMC Evol Biol 2011; 11:48. [PMID: 21332997 PMCID: PMC3049142 DOI: 10.1186/1471-2148-11-48] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2010] [Accepted: 02/18/2011] [Indexed: 01/17/2023] Open
Abstract
Background Disentangling the roles of geography and ecology driving population divergence and distinguishing adaptive from neutral evolution at the molecular level have been common goals among evolutionary and conservation biologists. Using single nucleotide polymorphism (SNP) multilocus genotypes for 31 sockeye salmon (Oncorhynchus nerka) populations from the Kvichak River, Alaska, we assessed the relative roles of geography (discrete boundaries or continuous distance) and ecology (spawning habitat and timing) driving genetic divergence in this species at varying spatial scales within the drainage. We also evaluated two outlier detection methods to characterize candidate SNPs responding to environmental selection, emphasizing which mechanism(s) may maintain the genetic variation of outlier loci. Results For the entire drainage, Mantel tests suggested a greater role of geographic distance on population divergence than differences in spawn timing when each variable was correlated with pairwise genetic distances. Clustering and hierarchical analyses of molecular variance indicated that the largest genetic differentiation occurred between populations from distinct lakes or subdrainages. Within one population-rich lake, however, Mantel tests suggested a greater role of spawn timing than geographic distance on population divergence when each variable was correlated with pairwise genetic distances. Variable spawn timing among populations was linked to specific spawning habitats as revealed by principal coordinate analyses. We additionally identified two outlier SNPs located in the major histocompatibility complex (MHC) class II that appeared robust to violations of demographic assumptions from an initial pool of eight candidates for selection. Conclusions First, our results suggest that geography and ecology have influenced genetic divergence between Alaskan sockeye salmon populations in a hierarchical manner depending on the spatial scale. Second, we found consistent evidence for diversifying selection in two loci located in the MHC class II by means of outlier detection methods; yet, alternative scenarios for the evolution of these loci were also evaluated. Both conclusions argue that historical contingency and contemporary adaptation have likely driven differentiation between Kvichak River sockeye salmon populations, as revealed by a suite of SNPs. Our findings highlight the need for conservation of complex population structure, because it provides resilience in the face of environmental change, both natural and anthropogenic.
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Hansen MHH, Young S, Jørgensen HBH, Pascal C, Henryon M, Seeb J. Assembling a dual purpose TaqMan-based panel of single-nucleotide polymorphism markers in rainbow trout and steelhead (Oncorhynchus mykiss) for association mapping and population genetics analysis. Mol Ecol Resour 2011; 11 Suppl 1:67-70. [PMID: 21429163 DOI: 10.1111/j.1755-0998.2010.02978.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Mette H H Hansen
- Institute of Genetics and Biotechnology, Faculty of Agricultural Sciences, Aarhus University, Denmark.
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Consuegra S, de Eyto E, McGinnity P, Stet RJ, Jordan WC. Contrasting responses to selection in class I and class IIα major histocompatibility-linked markers in salmon. Heredity (Edinb) 2011; 107:143-54. [PMID: 21266985 DOI: 10.1038/hdy.2010.177] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Comparison of levels and patterns of genetic variation in natural populations either across loci or against neutral expectation can yield insight into locus-specific differences in the strength and direction of evolutionary forces. We used both approaches to test the hypotheses on patterns of selection on major histocompatibility (MH)-linked markers. We performed temporal analyses of class I and class IIα MH-linked markers and eight microsatellite loci in two Atlantic salmon populations in Ireland on two temporal scales: over six decades and 9 years in the rivers Burrishoole and Delphi, respectively. We also compared contemporary Burrishoole and Delphi samples with nearby populations for the same loci. On comparing patterns of temporal and spatial differentiation among classes of loci, the class IIα MH-linked marker was consistently identified as an outlier compared with patterns at the other microsatellite loci or neutral expectation. We found higher levels of temporal and spatial heterogeneity in heterozygosity (but not in allelic richness) for the class IIα MH-linked marker compared with microsatellites. Tests on both within- and among-population differentiation are consistent with directional selection acting on the class IIα-linked marker in both temporal and spatial comparisons, but only in temporal comparisons for the class I-linked marker. Our results indicate a complex pattern of selection on MH-linked markers in natural populations of Atlantic salmon. These findings highlight the importance of considering selection on MH-linked markers when using these markers for management and conservation purposes.
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