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Bechsgaard J, Jorgensen TH, Jønsson AK, Schou M, Bilde T. Impaired immune function accompanies social evolution in spiders. Biol Lett 2022; 18:20220331. [PMID: 36541093 PMCID: PMC9768628 DOI: 10.1098/rsbl.2022.0331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
An efficient immune system is essential to the survival of many animals. Sociality increases risk of pathogen transmission, which should select for enhanced immune function. However, two hypotheses instead predict a weakened immune function: relaxed selection caused by social immunity/protection, and reduced efficacy of selection due to inbreeding, reproductive skew and female bias in social species that reduce effective population size and accelerate genetic drift. We assessed the effect of social evolution on immune function in a comparative study of two social spider species and their closely related subsocial sister species (genus Stegodyphus). The haemolymph of social species was less efficient in inhibiting bacterial growth of the potentially pathogenic bacteria Bacillus subtilis than that of subsocial species. Reduced efficacy of selection in social species was supported by comparative genomic analysis showing substantially elevated non-synonymous substitutions in immune genes in one of the social species. We propose that impaired immune function results from reduced efficacy of selection because the evolution of sociality in spiders is accompanied by demographic processes that elevate genetic drift. Positive feedback between pathogen-induced local extinctions and the resulting elevation of genetic drift may further weaken responses to selection by pathogens, and threaten species persistence.
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Affiliation(s)
| | | | | | - Mads Schou
- Department of Biology, Lund University, Lund, Sweden
| | - Trine Bilde
- Department of Biology, Aarhus University, Aarhus, Denmark
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2
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Charmouh AP, Reid JM, Bilde T, Bocedi G. Eco-evolutionary extinction and recolonization dynamics reduce genetic load and increase time to extinction in highly inbred populations. Evolution 2022; 76:2482-2497. [PMID: 36117269 PMCID: PMC9828521 DOI: 10.1111/evo.14620] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 06/01/2022] [Accepted: 07/11/2022] [Indexed: 01/22/2023]
Abstract
Understanding how genetic and ecological effects can interact to shape genetic loads within and across local populations is key to understanding ongoing persistence of systems that should otherwise be susceptible to extinction through mutational meltdown. Classic theory predicts short persistence times for metapopulations comprising small local populations with low connectivity, due to accumulation of deleterious mutations. Yet, some such systems have persisted over evolutionary time, implying the existence of mechanisms that allow metapopulations to avoid mutational meltdown. We first hypothesize a mechanism by which the combination of stochasticity in the numbers and types of mutations arising locally (genetic stochasticity), resulting local extinction, and recolonization through evolving dispersal facilitates metapopulation persistence. We then test this mechanism using a spatially and genetically explicit individual-based model. We show that genetic stochasticity in highly structured metapopulations can result in local extinctions, which can favor increased dispersal, thus allowing recolonization of empty habitat patches. This causes fluctuations in metapopulation size and transient gene flow, which reduces genetic load and increases metapopulation persistence over evolutionary time. Our suggested mechanism and simulation results provide an explanation for the conundrum presented by the continued persistence of highly structured populations with inbreeding mating systems that occur in diverse taxa.
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Affiliation(s)
- Anders P. Charmouh
- School of Biological SciencesUniversity of AberdeenAberdeenAB24 2TZUnited Kingdom
| | - Jane M. Reid
- School of Biological SciencesUniversity of AberdeenAberdeenAB24 2TZUnited Kingdom,Centre for Biodiversity DynamicsInstitutt for Biologi, NTNUTrondheim7491Norway
| | - Trine Bilde
- Department of BiologyAarhus UniversityAarhus C8000Denmark
| | - Greta Bocedi
- School of Biological SciencesUniversity of AberdeenAberdeenAB24 2TZUnited Kingdom
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3
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Aagaard A, Liu S, Tregenza T, Braad Lund M, Schramm A, Verhoeven KJF, Bechsgaard J, Bilde T. Adapting to climate with limited genetic diversity: Nucleotide, DNA methylation and microbiome variation among populations of the social spider Stegodyphus dumicola. Mol Ecol 2022; 31:5765-5783. [PMID: 36112081 PMCID: PMC9827990 DOI: 10.1111/mec.16696] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 09/01/2022] [Accepted: 09/06/2022] [Indexed: 02/06/2023]
Abstract
Understanding the role of genetic and nongenetic variants in modulating phenotypes is central to our knowledge of adaptive responses to local conditions and environmental change, particularly in species with such low population genetic diversity that it is likely to limit their evolutionary potential. A first step towards uncovering the molecular mechanisms underlying population-specific responses to the environment is to carry out environmental association studies. We associated climatic variation with genetic, epigenetic and microbiome variation in populations of a social spider with extremely low standing genetic diversity. We identified genetic variants that are associated strongly with environmental variation, particularly with average temperature, a pattern consistent with local adaptation. Variation in DNA methylation in many genes was strongly correlated with a wide set of climate parameters, thereby revealing a different pattern of associations than that of genetic variants, which show strong correlations to a more restricted range of climate parameters. DNA methylation levels were largely independent of cis-genetic variation and of overall genetic population structure, suggesting that DNA methylation can work as an independent mechanism. Microbiome composition also correlated with environmental variation, but most strong associations were with precipitation-related climatic factors. Our results suggest a role for both genetic and nongenetic mechanisms in shaping phenotypic responses to local environments.
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Affiliation(s)
- Anne Aagaard
- Section for Genetics, Ecology & Evolution, Department of BiologyAarhus UniversityAarhus CDenmark
| | - Shenglin Liu
- Section for Genetics, Ecology & Evolution, Department of BiologyAarhus UniversityAarhus CDenmark
| | - Tom Tregenza
- Centre for Ecology & Conservation, School of BiosciencesUniversity of ExeterPenryn CampusUK
| | - Marie Braad Lund
- Section for Microbiology, Department of BiologyAarhus UniversityAarhus CDenmark
| | - Andreas Schramm
- Section for Microbiology, Department of BiologyAarhus UniversityAarhus CDenmark
| | - Koen J. F. Verhoeven
- Terrestrial Ecology DepartmentNetherlands Institute of Ecology (NIOO‐KNAW)WageningenThe Netherlands
| | - Jesper Bechsgaard
- Section for Genetics, Ecology & Evolution, Department of BiologyAarhus UniversityAarhus CDenmark
| | - Trine Bilde
- Section for Genetics, Ecology & Evolution, Department of BiologyAarhus UniversityAarhus CDenmark
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4
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Parthasarathy B, Müller M, Bilde T, Schneider JM. Hunger state and not personality determines task participation in a spider society. Anim Behav 2022. [DOI: 10.1016/j.anbehav.2022.06.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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5
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Pilger TJ, Gido KB, Propst DL, Whitney JE, Turner TF. Demography predicts genetic effective size in a desert stream fish community. Am Nat 2022; 200:275-291. [DOI: 10.1086/720208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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6
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Busck MM, Lund MB, Bird TL, Bechsgaard JS, Bilde T, Schramm A. Temporal and spatial microbiome dynamics across natural populations of the social spider Stegodyphus dumicola. FEMS Microbiol Ecol 2022; 98:6526868. [PMID: 35147190 DOI: 10.1093/femsec/fiac015] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 01/07/2022] [Accepted: 02/09/2022] [Indexed: 11/13/2022] Open
Abstract
Host symbiont interactions may form obligatory or facultative associations that are context dependent. Long-term studies on microbiome composition from wild populations should assess the temporal and spatial dynamics of host-microbe associations. We characterized the temporal and spatial variation in the bacterial microbiome composition in six populations of the social spider Stegodyphus dumicola for 2.5 years, using 16S rRNA gene amplicon sequencing of whole spiders. Individuals within a nest exhibit highly similar microbiomes, which remain stable over several generations and are not predictably affected by seasonal variation in temperature or humidity. This stability in nest microbiome is likely due to social transmission, whereas drift-like processes during new nest foundations explain variation in host microbiomes between nests. This is supported by the lack of obligate symbionts (i.e. no symbionts are present in all spider individuals). Quantitative PCR analyses showed that the bacterial load of individual spiders is stable in healthy nests but can increase dramatically in perishing nests. These increases are not driven by specific bacterial taxa but likely caused by loss of host immune control under deteriorating conditions. Spider nests show an annual survival rate of approximately 45%, but nest death is not correlated to microbiome composition, and the bacteria found in S. dumicola are not considered to be high virulence pathogens.
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Affiliation(s)
- Mette M Busck
- Section for Microbiology, Department of Biology, Aarhus University, Aarhus, Denmark
| | - Marie B Lund
- Section for Microbiology, Department of Biology, Aarhus University, Aarhus, Denmark
| | - Tharina L Bird
- Department of Biological Sciences and Biotechnology, Botswana International University of Science and Technology (BIUST), Botswana.,Section for Genetics, Ecology and Evolution, Department of Biology, Aarhus University, Aarhus, Denmark.,General Entomology, Ditsong National Museum of Natural History, Pretoria, South Africa.,Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
| | - Jesper S Bechsgaard
- Section for Genetics, Ecology and Evolution, Department of Biology, Aarhus University, Aarhus, Denmark
| | - Trine Bilde
- Section for Genetics, Ecology and Evolution, Department of Biology, Aarhus University, Aarhus, Denmark
| | - Andreas Schramm
- Section for Microbiology, Department of Biology, Aarhus University, Aarhus, Denmark
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7
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Lammers A, Zweers H, Sandfeld T, Bilde T, Garbeva P, Schramm A, Lalk M. Antimicrobial Compounds in the Volatilome of Social Spider Communities. Front Microbiol 2021; 12:700693. [PMID: 34504476 PMCID: PMC8422909 DOI: 10.3389/fmicb.2021.700693] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Accepted: 07/31/2021] [Indexed: 11/24/2022] Open
Abstract
Social arthropods such as termites, ants, and bees are among others the most successful animal groups on earth. However, social arthropods face an elevated risk of infections due to the dense colony structure, which facilitates pathogen transmission. An interesting hypothesis is that social arthropods are protected by chemical compounds produced by the arthropods themselves, microbial symbionts, or plants they associate with. Stegodyphus dumicola is an African social spider species, inhabiting communal silk nests. Because of the complex three-dimensional structure of the spider nest antimicrobial volatile organic compounds (VOCs) are a promising protection against pathogens, because of their ability to diffuse through air-filled pores. We analyzed the volatilomes of S. dumicola, their nests, and capture webs in three locations in Namibia and assessed their antimicrobial potential. Volatilomes were collected using polydimethylsiloxane (PDMS) tubes and analyzed using GC/Q-TOF. We showed the presence of 199 VOCs and tentatively identified 53 VOCs. More than 40% of the tentatively identified VOCs are known for their antimicrobial activity. Here, six VOCs were confirmed by analyzing pure compounds namely acetophenone, 1,3-benzothiazole, 1-decanal, 2-decanone, 1-tetradecene, and docosane and for five of these compounds the antimicrobial activity were proven. The nest and web volatilomes had many VOCs in common, whereas the spider volatilomes were more differentiated. Clear differences were identified between the volatilomes from the different sampling sites which is likely justified by differences in the microbiomes of the spiders and nests, the plants, and the different climatic conditions. The results indicate the potential relevance of the volatilomes for the ecological success of S. dumicola.
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Affiliation(s)
- Alexander Lammers
- Department of Cellular Biochemistry and Metabolomics, University of Greifswald, Greifswald, Germany.,Department of Microbial Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, Netherlands
| | - Hans Zweers
- Department of Microbial Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, Netherlands
| | - Tobias Sandfeld
- Section for Microbiology, Department of Biology, Aarhus University, Aarhus, Denmark
| | - Trine Bilde
- Section for Genetics, Ecology and Evolution, Department of Biology, Aarhus University, Aarhus, Denmark
| | - Paolina Garbeva
- Department of Microbial Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, Netherlands
| | - Andreas Schramm
- Section for Microbiology, Department of Biology, Aarhus University, Aarhus, Denmark
| | - Michael Lalk
- Department of Cellular Biochemistry and Metabolomics, University of Greifswald, Greifswald, Germany
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8
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The bacterial and fungal nest microbiomes in populations of the social spider Stegodyphus dumicola. Syst Appl Microbiol 2021; 44:126222. [PMID: 34146923 DOI: 10.1016/j.syapm.2021.126222] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 05/09/2021] [Accepted: 05/26/2021] [Indexed: 12/17/2022]
Abstract
Social spiders of the species Stegodyphus dumicola live in communal nests with hundreds of individuals and are characterized by extremely low species-wide genetic diversity. The lack of genetic diversity in combination with group living imposes a potential threat for infection by pathogens. We therefore proposed that specific microbial symbionts inhabiting the spider nests may provide antimicrobial defense. To compare the bacterial and fungal diversity in 17 nests from three different locations in Namibia, we used 16S rRNA gene and internal transcribed spacer (ITS2) sequencing. The nest microbiomes differed between geographically distinct spider populations and appeared largely determined by the local environment. Nevertheless, we identified a core microbiome consisting of four bacterial genera (Curtobacterium, Modestobacter, Sphingomonas, Massilia) and four fungal genera (Aureobasidium, Didymella, Alternaria, Ascochyta), which likely are selected from surrounding soil and plants by the nest environment. We did not find indications for a strain- or species-specific symbiosis in the nests. Isolation of bacteria and fungi from nest material retrieved a few bacterial strains with antimicrobial activity but a number of antimicrobial fungi, including members of the fungal core microbiome. The significance of antimicrobial taxa in the nest microbiome for host protection remains to be shown.
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9
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Huang R, Zhang ZD, Wang Y, Wang YQ. Genetic variation and genetic structure within metapopulations of two closely related selfing and outcrossing Zingiber species (Zingiberaceae). AOB PLANTS 2021; 13:plaa065. [PMID: 33442464 PMCID: PMC7788390 DOI: 10.1093/aobpla/plaa065] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Accepted: 11/30/2020] [Indexed: 05/31/2023]
Abstract
Habitat fragmentation strongly affects the genetic diversity of plant populations, and this has always attracted much research interest. Although numerous studies have investigated the effects of habitat fragmentation on the genetic diversity of plant populations, fewer studies have compared species with contrasting breeding systems while accounting for phylogenetic distance. Here, we compare the levels of genetic diversity and differentiation within and among subpopulations in metapopulations (at fine-scale level) of two closely related Zingiber species, selfing Zingiber corallinum and outcrossing Zingiber nudicarpum. Comparisons of the genetic structure of species from unrelated taxa may be confounded by the effects of correlated ecological traits or/and phylogeny. Thus, we possibly reveal the differences in genetic diversity and spatial distribution of genetic variation within metapopulations that relate to mating systems. Compared to outcrossing Z. nudicarpum, the subpopulation genetic diversity in selfing Z. corallinum was significantly lower, but the metapopulation genetic diversity was not different. Most genetic variation resided among subpopulations in selfing Z. corallinum metapopulations, while a significant portion of variation resided either within or among subpopulations in outcrossing Z. nudicarpum, depending on whether the degree of subpopulation isolation surpasses the dispersal ability of pollen and seed. A stronger spatial genetic structure appeared within subpopulations of selfing Z. corallinum potentially due to restricted pollen flow and seed dispersal. In contrast, a weaker genetic structure was apparent in subpopulations of outcrossing Z. nudicarpum most likely caused by extensive pollen movement. Our study shows that high genetic variation can be maintained within metapopulations of selfing Zingiber species, due to increased genetic differentiation intensified primarily by the stochastic force of genetic drift among subpopulations. Therefore, maintenance of natural variability among subpopulations in fragmented areas is key to conserve the full range of genetic diversity of selfing Zingiber species. For outcrossing Zingiber species, maintenance of large populations is an important factor to enhance genetic diversity. Compared to outcrossing Z. nudicarpum, the subpopulation genetic diversity in selfing Z. corallinum was significantly lower, but the metapopulation genetic diversity did not differ. Most genetic variation resided among subpopulations in selfing Z. corallinum metapopulations, while a significant portion of variation resided either within or among subpopulations in outcrossing Z. nudicarpum, depending on whether the degree of subpopulation isolation surpasses the dispersal ability of pollen and seed. Our study shows that selfing Z. corallinum could maintain high genetic diversity through differentiation intensified primarily by the stochastic force of genetic drift among subpopulations at fine-scale level, but not local adaptation.
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Affiliation(s)
- Rong Huang
- Guangdong Provincial Key Laboratory of Biotechnology for Plant Development, School of Life Sciences, South China Normal University, Guangzhou, China
| | - Zong-Dian Zhang
- Guangdong Provincial Key Laboratory of Biotechnology for Plant Development, School of Life Sciences, South China Normal University, Guangzhou, China
| | - Yu Wang
- Guangdong Provincial Key Laboratory of Biotechnology for Plant Development, School of Life Sciences, South China Normal University, Guangzhou, China
| | - Ying-Qiang Wang
- Guangdong Provincial Key Laboratory of Biotechnology for Plant Development, School of Life Sciences, South China Normal University, Guangzhou, China
- Guangzhou Key Laboratory of Subtropical Biodiversity and Biomonitoring, School of Life Sciences, South China Normal University, Guangzhou, China
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10
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Busck MM, Settepani V, Bechsgaard J, Lund MB, Bilde T, Schramm A. Microbiomes and Specific Symbionts of Social Spiders: Compositional Patterns in Host Species, Populations, and Nests. Front Microbiol 2020; 11:1845. [PMID: 32849442 PMCID: PMC7412444 DOI: 10.3389/fmicb.2020.01845] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Accepted: 07/14/2020] [Indexed: 12/18/2022] Open
Abstract
Social spiders have remarkably low species-wide genetic diversities, potentially increasing the relative importance of microbial symbionts for host fitness. Here we explore the bacterial microbiomes of three species of social Stegodyphus (S. dumicola, S. mimosarum, and S. sarasinorum), within and between populations, using 16S rRNA gene amplicon sequencing. The microbiomes of the three spider species were distinct but shared similarities in membership and structure. This included low overall diversity (Shannon index 0.5–1.7), strong dominance of single symbionts in individual spiders (McNaughton’s dominance index 0.68–0.93), and a core microbiome (>50% prevalence) consisting of 5–7 specific symbionts. The most abundant and prevalent symbionts were classified as Chlamydiales, Borrelia, and Mycoplasma, all representing novel, presumably Stegodyphus-specific lineages. Borrelia- and Mycoplasma-like symbionts were localized by fluorescence in situ hybridization (FISH) in the spider midgut. The microbiomes of individual spiders were highly similar within nests but often very different between nests from the same population, with only the microbiome of S. sarasinorum consistently reflecting host population structure. The weak population pattern in microbiome composition renders microbiome-facilitated local adaptation unlikely. However, the retention of specific symbionts across populations and species may indicate a recurrent acquisition from environmental vectors or an essential symbiotic contribution to spider phenotype.
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Affiliation(s)
- Mette Marie Busck
- Section for Microbiology, Department of Biology, Aarhus University, Aarhus, Denmark
| | - Virginia Settepani
- Section for Genetics, Ecology and Evolution, Department of Biology, Aarhus University, Aarhus, Denmark
| | - Jesper Bechsgaard
- Section for Genetics, Ecology and Evolution, Department of Biology, Aarhus University, Aarhus, Denmark
| | - Marie Braad Lund
- Section for Microbiology, Department of Biology, Aarhus University, Aarhus, Denmark
| | - Trine Bilde
- Section for Genetics, Ecology and Evolution, Department of Biology, Aarhus University, Aarhus, Denmark
| | - Andreas Schramm
- Section for Microbiology, Department of Biology, Aarhus University, Aarhus, Denmark
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11
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Botham JL, Haddad CR, Gryzenhout M, Swart VR, Bredenhand E. High genetic diversity of spider species in a mosaic montane grassland landscape. PLoS One 2020; 15:e0234437. [PMID: 32511281 PMCID: PMC7279597 DOI: 10.1371/journal.pone.0234437] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Accepted: 05/25/2020] [Indexed: 11/19/2022] Open
Abstract
Gene flow and genetic variation were examined within and among populations of five of the most common spider species in shrublands of the mountainous Golden Gate Highlands National Park (GGHNP), South Africa. These species included three active hunters, Dendryphantes purcelli Peckham & Peckham, 1903 (Salticidae), Pherecydes tuberculatus O.P.-Cambridge, 1883 (Thomisidae) and Philodromus browningi Lawrence, 1952 (Philodromidae), and two web-builders, Neoscona subfusca (C.L. Koch, 1837) (Araneidae) and a Theridion Walckenaer, 1802 species (Theridiidae). A total of 249 spiders (57 D. purcelli, 69 N. subfusca, 34 P. browningi, 56 P. tuberculatus and 33 Theridion sp.) were collected and analysed from six shrubland localities in the park. Analyses of sequence variation of the mitochondrial cytochrome oxidase c subunit I (COI) gene for each species revealed relatively low nucleotide diversity (π < 0.0420) but high genetic diversity (Hd > 0.6500) within populations for all species, except P. tuberculatus. Genetic differentiation was also noted to differ between species, with only P. tuberculatus indicating very large divergence (Fst > 0.2500). These results were reflected by gene flow, with D. purcelli, N. subfusca and the Theridion sp. estimated as experiencing more than one disperser per generation. Overall, highest gene flow was found in the two web-building species, indicating possible high dispersal ability of these spiders in the GGHNP. Additionally, constructed phylogenies indicated possible cryptic speciation occurring in the majority of the investigated species. Our current results indicate that the five investigated spider species were able to maintain gene flow between shrubland populations within the GGHNP to some degree, despite the mountainous landscape. However, further analyses incorporating additional molecular markers are needed to properly determine the extent of genetic diversity and gene flow of these species within the GGHNP.
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Affiliation(s)
- Jason L. Botham
- Department of Zoology and Entomology, University of the Free State, Bloemfontein, Free State, South Africa
- * E-mail:
| | - Charles R. Haddad
- Department of Zoology and Entomology, University of the Free State, Bloemfontein, Free State, South Africa
| | - Marieka Gryzenhout
- Department of Genetics, University of the Free State, Bloemfontein, Free State, South Africa
| | - Vaughn R. Swart
- Department of Zoology and Entomology, University of the Free State, Bloemfontein, Free State, South Africa
| | - Emile Bredenhand
- Department of Zoology and Entomology, University of the Free State Qwaqwa Campus, Phuthaditjhaba, Free State, South Africa
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12
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Tong C, Najm GM, Pinter-Wollman N, Pruitt JN, Linksvayer TA. Comparative Genomics Identifies Putative Signatures of Sociality in Spiders. Genome Biol Evol 2020; 12:122-133. [PMID: 31960912 PMCID: PMC7108510 DOI: 10.1093/gbe/evaa007] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/15/2020] [Indexed: 12/15/2022] Open
Abstract
Comparative genomics has begun to elucidate the genomic basis of social life in insects, but insight into the genomic basis of spider sociality has lagged behind. To begin, to characterize genomic signatures associated with the evolution of social life in spiders, we performed one of the first spider comparative genomics studies including five solitary species and two social species, representing two independent origins of sociality in the genus Stegodyphus. We found that the two social spider species had a large expansion of gene families associated with transport and metabolic processes and an elevated genome-wide rate of molecular evolution compared with the five solitary spider species. Genes that were rapidly evolving in the two social species relative to the five solitary species were enriched for transport, behavior, and immune functions, whereas genes that were rapidly evolving in the solitary species were enriched for energy metabolism processes. Most rapidly evolving genes in the social species Stegodyphus dumicola were broadly expressed across four tissues and enriched for transport functions, but 12 rapidly evolving genes showed brain-specific expression and were enriched for social behavioral processes. Altogether, our study identifies putative genomic signatures and potential candidate genes associated with spider sociality. These results indicate that future spider comparative genomic studies, including broader sampling and additional independent origins of sociality, can further clarify the genomic causes and consequences of social life.
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Affiliation(s)
- Chao Tong
- Department of Biology, University of Pennsylvania
| | - Gabriella M Najm
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles
| | - Noa Pinter-Wollman
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles
| | - Jonathan N Pruitt
- Department of Psychology, Neurobiology & Behaviour, McMaster University, Hamilton, Ontario, Canada
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13
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Tuni C, Mestre L, Berger-Tal R, Lubin Y, Bilde T. Mate choice in naturally inbred spiders: testing the role of relatedness. Anim Behav 2019. [DOI: 10.1016/j.anbehav.2019.08.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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14
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Bechsgaard J, Schou MF, Vanthournout B, Hendrickx F, Knudsen B, Settepani V, Schierup MH, Bilde T. Evidence for Faster X Chromosome Evolution in Spiders. Mol Biol Evol 2019; 36:1281-1293. [PMID: 30912801 PMCID: PMC6526907 DOI: 10.1093/molbev/msz074] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
In species with chromosomal sex determination, X chromosomes are predicted to evolve faster than autosomes because of positive selection on recessive alleles or weak purifying selection. We investigated X chromosome evolution in Stegodyphus spiders that differ in mating system, sex ratio, and population dynamics. We assigned scaffolds to X chromosomes and autosomes using a novel method based on flow cytometry of sperm cells and reduced representation sequencing. We estimated coding substitution patterns (dN/dS) in a subsocial outcrossing species (S. africanus) and its social inbreeding and female-biased sister species (S. mimosarum), and found evidence for faster-X evolution in both species. X chromosome-to-autosome diversity (piX/piA) ratios were estimated in multiple populations. The average piX/piA estimates of S. africanus (0.57 [95% CI: 0.55-0.60]) was lower than the neutral expectation of 0.75, consistent with more hitchhiking events on X-linked loci and/or a lower X chromosome mutation rate, and we provide evidence in support of both. The social species S. mimosarum has a significantly higher piX/piA ratio (0.72 [95% CI: 0.65-0.79]) in agreement with its female-biased sex ratio. Stegodyphus mimosarum also have different piX/piA estimates among populations, which we interpret as evidence for recurrent founder events. Simulations show that recurrent founder events are expected to decrease the piX/piA estimates in S. mimosarum, thus underestimating the true effect of female-biased sex ratios. Finally, we found lower synonymous divergence on X chromosomes in both species, and the male-to-female substitution ratio to be higher than 1, indicating a higher mutation rate in males.
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Affiliation(s)
| | - Mads Fristrup Schou
- Department of Bioscience, Aarhus University, Aarhus C, Denmark.,Department of Biology, Lund University, SE-223 62 Lund, Sweden
| | - Bram Vanthournout
- Department of Bioscience, Aarhus University, Aarhus C, Denmark.,Evolution and Optics of Nanostructure Group (EON), Biology Department, Ghent University, Ghent, Belgium
| | - Frederik Hendrickx
- Royal Belgian Institute of Natural Sciences, Brussels, Belgium.,Terrestrial Ecology Unit (TEREC), Biology Department, Ghent University, Ghent, Belgium
| | | | | | - Mikkel Heide Schierup
- Department of Bioscience, Aarhus University, Aarhus C, Denmark.,Bioinformatics Research Centre (BiRC), Aarhus University, Aarhus C, Denmark
| | - Trine Bilde
- Department of Bioscience, Aarhus University, Aarhus C, Denmark
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15
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Liu S, Aageaard A, Bechsgaard J, Bilde T. DNA Methylation Patterns in the Social Spider, Stegodyphus dumicola. Genes (Basel) 2019; 10:E137. [PMID: 30759892 PMCID: PMC6409797 DOI: 10.3390/genes10020137] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 01/25/2019] [Accepted: 01/25/2019] [Indexed: 12/18/2022] Open
Abstract
Variation in DNA methylation patterns among genes, individuals, and populations appears to be highly variable among taxa, but our understanding of the functional significance of this variation is still incomplete. We here present the first whole genome bisulfite sequencing of a chelicerate species, the social spider Stegodyphus dumicola. We show that DNA methylation occurs mainly in CpG context and is concentrated in genes. This is a pattern also documented in other invertebrates. We present RNA sequence data to investigate the role of DNA methylation in gene regulation and show that, within individuals, methylated genes are more expressed than genes that are not methylated and that methylated genes are more stably expressed across individuals than unmethylated genes. Although no causal association is shown, this lends support for the implication of DNA CpG methylation in regulating gene expression in invertebrates. Differential DNA methylation between populations showed a small but significant correlation with differential gene expression. This is consistent with a possible role of DNA methylation in local adaptation. Based on indirect inference of the presence and pattern of DNA methylation in chelicerate species whose genomes have been sequenced, we performed a comparative phylogenetic analysis. We found strong evidence for exon DNA methylation in the horseshoe crab Limulus polyphemus and in all spider and scorpion species, while most Parasitiformes and Acariformes species seem to have lost DNA methylation.
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Affiliation(s)
- Shenglin Liu
- Department of Bioscience, Aarhus University, 8000 Aarhus C, Denmark.
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16
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Lichtenstein JLL, Kamath A, Bengston S, Avilés L, Pruitt JN. Female-Biased Sex Ratios Increase Colony Survival and Reproductive Output in the Spider Anelosimus studiosus. Am Nat 2018; 192:552-563. [PMID: 30332581 DOI: 10.1086/699838] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Negative frequency-dependent selection acting on the sexes is hypothesized to drive populations toward a balanced sex ratio. However, numerous examples of female-biased sex ratios pepper the arthropods. Theoretical examinations have proposed that female-biased populations or groups can have higher chances of surviving and propagating that may be advantageous. We evaluated this hypothesis in the semisocial spider Anelosimus studiosus by creating artificial colonies of varying sex ratios and sizes and observing colony performance at sites with high versus low group extinction rates. We also tested whether colony extinction rates and sex ratios were correlated across 25 collection sites, spanning 10° latitude. We found that colonies with female-biased sex ratios produced more egg cases and were more likely to survive the duration of a field season, suggesting that female-biased sex ratios confer both survival and reproductive advantages on colonies. The effect of sex ratio on colony survival and reproductive output was strongest for small colonies in high extinction areas. Moreover, we found that female-biased sex ratios correlated with greater extinction rates across 25 sites, indicating that female-biased sex ratios may have evolved at some sites in response to high extinction rates. These findings suggest that selection favoring groups with female-biased sex ratios may operate in A. studiosus, shedding light on some of the factors that may drive the evolution of biased sex ratios.
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17
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18
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Junghanns A, Holm C, Schou MF, Sørensen AB, Uhl G, Bilde T. Extreme allomaternal care and unequal task participation by unmated females in a cooperatively breeding spider. Anim Behav 2017. [DOI: 10.1016/j.anbehav.2017.08.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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19
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Settepani V, Schou MF, Greve M, Grinsted L, Bechsgaard J, Bilde T. Evolution of sociality in spiders leads to depleted genomic diversity at both population and species levels. Mol Ecol 2017; 26:4197-4210. [DOI: 10.1111/mec.14196] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Revised: 04/06/2017] [Accepted: 04/10/2017] [Indexed: 12/21/2022]
Affiliation(s)
- V. Settepani
- Department of Bioscience; Aarhus University; Aarhus C Denmark
| | - M. F. Schou
- Department of Bioscience; Aarhus University; Aarhus C Denmark
| | - M. Greve
- Department of Plant Science; University of Pretoria; Hatfield South Africa
| | - L. Grinsted
- School of Biological Sciences; Royal Holloway University of London; Egham UK
| | - J. Bechsgaard
- Department of Bioscience; Aarhus University; Aarhus C Denmark
| | - T. Bilde
- Department of Bioscience; Aarhus University; Aarhus C Denmark
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20
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Smith DR, Su YC, Berger-Tal R, Lubin Y. Population genetic evidence for sex-specific dispersal in an inbred social spider. Ecol Evol 2016; 6:5479-90. [PMID: 27551398 PMCID: PMC4984519 DOI: 10.1002/ece3.2200] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Revised: 04/29/2016] [Accepted: 05/02/2016] [Indexed: 11/08/2022] Open
Abstract
Dispersal in most group-living species ensures gene flow among groups, but in cooperative social spiders, juvenile dispersal is suppressed and colonies are highly inbred. It has been suggested that such inbred sociality is advantageous in the short term, but likely to lead to extinction or reduced speciation rates in the long run. In this situation, very low levels of dispersal and gene flow among colonies may have unusually important impacts on fitness and persistence of social spiders. We investigated sex-specific differences in dispersal and gene flow among colonies, as reflected in the genetic structure within colonies and populations of the African social spider Stegodyphus dumicola Pocock, 1898 (Eresidae). We used DNA fingerprinting and mtDNA sequence data along with spatial mapping of colonies to compare male and female patterns of relatedness within and among colonies at three study sites. Samples were collected during and shortly after the mating season to detect sex-specific dispersal. Distribution of mtDNA haplotypes was consistent with proliferation of social nests by budding and medium- to long-distance dispersal by ballooning females. Analysis of molecular variance and spatial autocorrelation analyses of AFLPs showed high levels of genetic similarity within colonies, and STRUCTURE analyses revealed that the number of source populations contributing to colonies ranged from one to three. We also showed significant evidence of male dispersal among colonies at one site. These results support the hypothesis that in social spiders, genetic cohesion among populations is maintained by long-distance dispersal of female colony founders. Genetic diversity within colonies is maintained by colony initiation by multiple dispersing females, and adult male dispersal over short distances. Male dispersal may be particularly important in maintaining gene flow among colonies in local populations.
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Affiliation(s)
- Deborah R Smith
- Department of Ecology & Evolutionary Biology University of Kansas Lawrence Kansas 66045
| | - Yong-Chao Su
- Department of Ecology & Evolutionary Biology University of Kansas Lawrence Kansas 66045; Biodiversity Institute University of Kansas Lawrence Kansas 66045
| | - Reut Berger-Tal
- Blaustein Institutes for Desert Research Ben-Gurion University of the Negev Sede Boqer Campus Midreshet Ben-Gurion 84990 Israel
| | - Yael Lubin
- Blaustein Institutes for Desert Research Ben-Gurion University of the Negev Sede Boqer Campus Midreshet Ben-Gurion 84990 Israel
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21
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Yang LN, Zhu W, Wu EJ, Yang C, Thrall PH, Burdon JJ, Jin LP, Shang LP, Zhan J. Trade-offs and evolution of thermal adaptation in the Irish potato famine pathogen Phytophthora infestans. Mol Ecol 2016; 25:4047-58. [PMID: 27288627 DOI: 10.1111/mec.13727] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Revised: 05/23/2016] [Accepted: 05/26/2016] [Indexed: 01/07/2023]
Abstract
Temperature is one of the most important environmental parameters with crucial impacts on nearly all biological processes. Due to anthropogenic activity, average air temperatures are expected to increase by a few degrees in coming decades, accompanied by an increased occurrence of extreme temperature events. Such global trends are likely to have various major impacts on human society through their influence on natural ecosystems, food production and biotic interactions, including diseases. In this study, we used a combination of statistical genetics, experimental evolution and common garden experiments to investigate the evolutionary potential for thermal adaptation in the potato late blight pathogen, Phytophthora infestans, and infer its likely response to changing temperatures. We found a trade-off associated with thermal adaptation to heterogeneous environments in P. infestans, with the degree of the trade-off peaking approximately at the pathogen's optimum growth temperature. A genetic trade-off in thermal adaptation was also evidenced by the negative association between a strain's growth rate and its thermal range for growth, and warm climates selecting for a low pathogen growth rate. We also found a mirror effect of phenotypic plasticity and genetic adaptation on growth rate. At below the optimum, phenotypic plasticity enhances pathogen's growth rate but nature selects for slower growing genotypes when temperature increases. At above the optimum, phenotypic plasticity reduces pathogen's growth rate but natural selection favours for faster growing genotypes when temperature increases further. We conclude from these findings that the growth rate of P. infestans will only be marginally affected by global warming.
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Affiliation(s)
- Li-Na Yang
- Fujian Key Lab of Plant Virology, Institute of Plant Virology, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Wen Zhu
- Fujian Key Lab of Plant Virology, Institute of Plant Virology, Fujian Agriculture and Forestry University, Fuzhou, China
| | - E-Jiao Wu
- Fujian Key Lab of Plant Virology, Institute of Plant Virology, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Ce Yang
- Fujian Key Lab of Plant Virology, Institute of Plant Virology, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Peter H Thrall
- CSIRO Agriculture, PO Box 1600, Canberra, Australian Capital Territory, 2601, Australia
| | - Jeremy J Burdon
- CSIRO Agriculture, PO Box 1600, Canberra, Australian Capital Territory, 2601, Australia
| | - Li-Ping Jin
- Institute of Flowers and Vegetables, Chinese Academy of Agricultural Sciences, Beijing, 100081, China
| | - Li-Ping Shang
- Fujian Key Lab of Plant Virology, Institute of Plant Virology, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Jiasui Zhan
- Key Lab for Biopesticide and Chemical Biology, Ministry of Education, Fujian Agriculture and Forestry University, Fuzhou, China
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22
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Vanthournout B, Greve M, Bruun A, Bechsgaard J, Overgaard J, Bilde T. Benefits of Group Living Include Increased Feeding Efficiency and Lower Mass Loss during Desiccation in the Social and Inbreeding Spider Stegodyphus dumicola. Front Physiol 2016; 7:18. [PMID: 26869936 PMCID: PMC4735397 DOI: 10.3389/fphys.2016.00018] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2015] [Accepted: 01/12/2016] [Indexed: 01/13/2023] Open
Abstract
Group living carries a price: it inherently entails increased competition for resources and reproduction, and may also be associated with mating among relatives, which carries costs of inbreeding. Nonetheless, group living and sociality is found in many animals, and understanding the direct and indirect benefits of cooperation that override the inherent costs remains a challenge in evolutionary ecology. Individuals in groups may benefit from more efficient management of energy or water reserves, for example in the form of reduced water or heat loss from groups of animals huddling, or through reduced energy demands afforded by shared participation in tasks. We investigated the putative benefits of group living in the permanently social spider Stegodyphus dumicola by comparing the effect of group size on standard metabolic rate, lipid/protein content as a body condition measure, feeding efficiency, per capita web investment, and weight/water loss and survival during desiccation. Because energetic expenditure is temperature sensitive, some assays were performed under varying temperature conditions. We found that feeding efficiency increased with group size, and the rate of weight loss was higher in solitary individuals than in animals in groups of various sizes during desiccation. Interestingly, this was not translated into differences in survival or in standard metabolic rate. We did not detect any group size effects for other parameters, and group size effects did not co-vary with experimental temperature in a predictive manner. Both feeding efficiency and mass loss during desiccation are relevant ecological factors as the former results in lowered predator exposure time, and the latter benefits social spiders which occupy arid, hot environments.
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Affiliation(s)
| | - Michelle Greve
- Department of Bioscience, Aarhus UniversityAarhus, Denmark; Department of Plant Science, University of PretoriaHatfield, South Africa
| | - Anne Bruun
- Department of Bioscience, Aarhus University Aarhus, Denmark
| | | | | | - Trine Bilde
- Department of Bioscience, Aarhus University Aarhus, Denmark
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23
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Settepani V, Bechsgaard J, Bilde T. Phylogenetic analysis suggests that sociality is associated with reduced effectiveness of selection. Ecol Evol 2016; 6:469-77. [PMID: 26843931 PMCID: PMC4729245 DOI: 10.1002/ece3.1886] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Accepted: 11/24/2015] [Indexed: 11/07/2022] Open
Abstract
The evolution of sociality in spiders is associated with female bias, reproductive skew and an inbreeding mating system, factors that cause a reduction in effective population size and increase effects of genetic drift. These factors act to decrease the effectiveness of selection, thereby increasing the fixation probability of deleterious mutations. Comparative studies of closely related species with contrasting social traits and mating systems provide the opportunity to test consequences of low effective population size on the effectiveness of selection empirically. We used phylogenetic analyses of three inbred social spider species and seven outcrossing subsocial species of the genus Stegodyphus, and compared dN/dS ratios and codon usage bias between social Inbreeding and subsocial outcrossing mating systems to assess the effectiveness of selection. The overall results do not differ significantly between the social inbreeding and outcrossing species, but suggest a tendency for lower codon usage bias and higher dN/dS ratios in the social inbreeding species compared with their outcrossing congeners. The differences in dN/dS ratio and codon usage bias between social and subsocial species are modest but consistent with theoretical expectations of reduced effectiveness of selection in species with relatively low effective population size. The modest differences are consistent with relatively recent evolution of social mating systems. Additionally, the short terminal branches and lack of speciation of the social lineages, together with low genetic diversity lend support for the transient state of permanent sociality in spiders.
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Affiliation(s)
- Virginia Settepani
- Department of BioscienceAarhus UniversityNy Munkegade 116, Building 15408000Aarhus CDenmark
| | - Jesper Bechsgaard
- Department of BioscienceAarhus UniversityNy Munkegade 116, Building 15408000Aarhus CDenmark
| | - Trine Bilde
- Department of BioscienceAarhus UniversityNy Munkegade 116, Building 15408000Aarhus CDenmark
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24
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Majer M, Svenning JC, Bilde T. Habitat productivity predicts the global distribution of social spiders. Front Ecol Evol 2015. [DOI: 10.3389/fevo.2015.00101] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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25
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Berger-Tal R, Lubin Y, Settepani V, Majer M, Bilde T, Tuni C. Evidence for loss of nepotism in the evolution of permanent sociality. Sci Rep 2015; 5:13284. [PMID: 26333675 PMCID: PMC4558611 DOI: 10.1038/srep13284] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2015] [Accepted: 07/23/2015] [Indexed: 11/09/2022] Open
Abstract
Kin selected benefits of cooperation result in pronounced kin discrimination and nepotism in many social species and favour the evolution of sociality. However, low variability in relatedness among group members, infrequent competitive interactions with non-relatives, and direct benefits of cooperation may relax selection for nepotism. We tested this prediction in a permanently social spider, Stegodyphus dumicola that appears to fulfil these conditions. Sociality is a derived trait, and kin discrimination exists in sub-social closely related congeners and is likely a selective force in the sub-social route to permanent sociality in spiders. We examined whether social spiders show nepotism in cooperative feeding when genetic relatedness among group members was experimentally varied. We found no effect of relatedness on feeding efficiency, growth rate or participation in feeding events. Previous studies on sub-social species showed benefits of communal feeding with kin, indicating nepotistic cooperation. The lack of evidence for nepotism in the social species suggests that kin discrimination has been lost or is irrelevant in communal feeding. Our results are consistent with the hypothesis that the role of nepotism is diminished when cooperation evolves in certain genetic and ecological contexts, e.g. when intra-group genetic relatedness is homogeneous and encounters with competitors are rare.
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Affiliation(s)
- Reut Berger-Tal
- Mitrani Department of Desert Ecology, Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben-Gurion, 84990, Israel
- Aarhus University, Department of Bioscience, Ny Munkegade 116, DK-8000 Aarhus C, Denmark
- BioCircuits Institute University of California, San Diego 9500 Gilman Drive, Mail Code 0328 La Jolla, CA 92093-0328, USA
| | - Yael Lubin
- Mitrani Department of Desert Ecology, Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben-Gurion, 84990, Israel
| | - Virginia Settepani
- Aarhus University, Department of Bioscience, Ny Munkegade 116, DK-8000 Aarhus C, Denmark
| | - Marija Majer
- Aarhus University, Department of Bioscience, Ny Munkegade 116, DK-8000 Aarhus C, Denmark
| | - Trine Bilde
- Aarhus University, Department of Bioscience, Ny Munkegade 116, DK-8000 Aarhus C, Denmark
| | - Cristina Tuni
- Aarhus University, Department of Bioscience, Ny Munkegade 116, DK-8000 Aarhus C, Denmark
- Ludwig Maximilians University Munich, Department Biology II, Großhaderner Str. 2, 82152 Planegg–Martinsried, Germany
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26
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Fountain T, Butlin RK, Reinhardt K, Otti O. Outbreeding effects in an inbreeding insect, Cimex lectularius. Ecol Evol 2014; 5:409-18. [PMID: 25691967 PMCID: PMC4314272 DOI: 10.1002/ece3.1373] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Revised: 11/17/2014] [Accepted: 11/17/2014] [Indexed: 11/12/2022] Open
Abstract
In some species, populations with few founding individuals can be resilient to extreme inbreeding. Inbreeding seems to be the norm in the common bed bug, Cimex lectularius, a flightless insect that, nevertheless, can reach large deme sizes and persist successfully. However, bed bugs can also be dispersed passively by humans, exposing inbred populations to gene flow from genetically distant populations. The introduction of genetic variation through this outbreeding could lead to increased fitness (heterosis) or be costly by causing a loss of local adaptation or exposing genetic incompatibility between populations (outbreeding depression). Here, we addressed how inbreeding within demes and outbreeding between distant populations impact fitness over two generations in this re-emerging public health pest. We compared fitness traits of families that were inbred (mimicking reproduction following a founder event) or outbred (mimicking reproduction following a gene flow event). We found that outbreeding led to increased starvation resistance compared to inbred families, but this benefit was lost after two generations of outbreeding. No other fitness benefits of outbreeding were observed in either generation, including no differences in fecundity between the two treatments. Resilience to inbreeding is likely to result from the history of small founder events in the bed bug. Outbreeding benefits may only be detectable under stress and when heterozygosity is maximized without disruption of coadaptation. We discuss the consequences of these results both in terms of inbreeding and outbreeding in populations with genetic and spatial structuring, as well as for the recent resurgence of bed bug populations.
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Affiliation(s)
- Toby Fountain
- Animal and Plant Sciences, University of Sheffield, Western Bank Sheffield, S10 2TN, UK ; Department of Biosciences, University of Helsinki PO Box 65 (Viikinkaari 1), FI-00014, Helsinki, Finland
| | - Roger K Butlin
- Animal and Plant Sciences, University of Sheffield, Western Bank Sheffield, S10 2TN, UK ; Sven Lovén Centre - Tjärnö, University of Gothenburg SE, 452 96, Strömstad, Sweden
| | - Klaus Reinhardt
- Animal and Plant Sciences, University of Sheffield, Western Bank Sheffield, S10 2TN, UK ; Institute for Evolution and Ecology, University of Tübingen Auf der Morgenstelle 28, D-72076, Tübingen, Germany
| | - Oliver Otti
- Animal and Plant Sciences, University of Sheffield, Western Bank Sheffield, S10 2TN, UK ; Animal Population Ecology, Animal Ecology I, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth Universitätsstrasse 30, 95440, Bayreuth, Germany
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