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Yukilevich R, Aoki F, Egan S, Zhang L. Coevolutionary Interactions between Sexual and Habitat Isolation during Reinforcement. Cold Spring Harb Perspect Biol 2024; 16:a041431. [PMID: 38316551 PMCID: PMC11065176 DOI: 10.1101/cshperspect.a041431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2024]
Abstract
Speciation often involves the evolution of multiple genetic-based barriers to gene flow (i.e., "coupling"). However, barriers may exhibit a diversity of evolutionary interactions during speciation. These dynamics are important in reinforcement, where selection may favor different prezygotic isolating barriers to avoid maladaptive hybridization. Here we study the interaction between evolution of sexual and habitat isolation. We first review the empirical literature where both barriers were explicitly considered, and then develop a population genetic model of reinforcement. Most studies of both sexual and habitat isolation were found in phytophagous insect systems. In 76% of these studies, both barriers coevolved; the remaining cases either showed only habitat isolation (21%) or only sexual isolation (3%). Our two-allele genetic mechanism model of each barrier also found that these often coevolved, but habitat isolation was generally more effective during reinforcement. Depending on the fitness of hybrids (e.g., Dobzhansky-Muller incompatibilities) and initial migration rate, these barriers could either facilitate, curtail, or have no effect on each other. This indicates that basic parameters will alter the underlying evolutionary dynamics, and thus the nature of "speciation coupling" will be highly variable in natural systems. Finally, we studied initially asymmetrical migration rates and found that populations with higher initial emigration evolved stronger habitat isolation, while populations that initially received more immigrants exhibited stronger sexual isolation. These results are in line with observations in some empirical studies, but more data is needed to test their generality.
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Affiliation(s)
- Roman Yukilevich
- Department of Biology, Union College, Integrated Science and Engineering Complex, Schenectady, New York 12308, USA
| | - Fumio Aoki
- Department of Ecology and Evolution, Stony Brook University, Stony Brook, New York 11794, USA
| | - Scott Egan
- Department of Biosciences, Rice University, Houston, Texas 77005, USA
| | - Linyi Zhang
- Department of Biological Sciences, George Washington University, Washington, D.C. 20052, USA
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Sianta SA, Moeller DA, Brandvain Y. The extent of introgression between incipient Clarkia species is determined by temporal environmental variation and mating system. Proc Natl Acad Sci U S A 2024; 121:e2316008121. [PMID: 38466849 PMCID: PMC10963018 DOI: 10.1073/pnas.2316008121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Accepted: 02/07/2024] [Indexed: 03/13/2024] Open
Abstract
Introgression is pervasive across the tree of life but varies across taxa, geography, and genomic regions. However, the factors modulating this variation and how they may be affected by global change are not well understood. Here, we used 200 genomes and a 15-y site-specific environmental dataset to investigate the effects of environmental variation and mating system divergence on the magnitude of introgression between a recently diverged outcrosser-selfer pair of annual plants in the genus Clarkia. These sister taxa diverged very recently and subsequently came into secondary sympatry where they form replicated contact zones. Consistent with observations of other outcrosser-selfer pairs, we found that introgression was asymmetric between taxa, with substantially more introgression from the selfer to the outcrosser. This asymmetry was caused by a bias in the direction of initial F1 hybrid formation and subsequent backcrossing. We also found extensive variation in the outcrosser's admixture proportion among contact zones, which was predicted nearly entirely by interannual variance in spring precipitation. Greater fluctuations in spring precipitation resulted in higher admixture proportions, likely mediated by the effects of spring precipitation on the expression of traits that determine premating reproductive isolation. Climate-driven hybridization dynamics may be particularly affected by global change, potentially reshaping species boundaries and adaptation to novel environments.
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Affiliation(s)
- Shelley A. Sianta
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, MN55108
| | - David A. Moeller
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, MN55108
| | - Yaniv Brandvain
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, MN55108
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3
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Roush AM, Zhang L, Hood GR, Ott JR, Egan SP. A test of trade-offs in dispersal and reproduction within and between a sister species pair of specialist insect herbivores. Oecologia 2024; 204:529-542. [PMID: 38324065 DOI: 10.1007/s00442-024-05512-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2023] [Accepted: 01/08/2024] [Indexed: 02/08/2024]
Abstract
Understanding the drivers of trade-offs among traits is vital for comprehending the evolution and maintenance of trait variation. Theoretical frameworks propose that evolutionary mechanisms governing trade-offs frequently exhibit a scale-dependent nature. However, empirical tests of whether trade-offs exhibited across various biological scales (i.e. individuals, populations, species, genera, etc.) remains scarce. In this study, we explore trade-off between dispersal and reproductive effort among sympatric sister species of wasps in the genus Belonocnema (Hymenoptera: Cynipini: Cynipidae) that form galls on live oaks: B. fossoria, which specializes on Quercus geminata, and B. treatae, which specializes on Q. virginiana. Specifically, our results suggest that B. fossoria has evolved reduced flight capability and smaller wings, but a larger abdomen and greater total reproductive effort than B. treatae, which has larger wings and is a stronger flier, but has a smaller abdomen and reduced total reproductive effort. These traits and the relationships among them remain unchanged when B. fossoria and B. treatae are transplanted and reared onto the alternative host plant, suggesting that trait divergence is genetically based as opposed to being a plastic response to the different rearing environments. However, when looking within species, we found no evidence of intraspecific trade-offs between wing length and reproductive traits within either B. fossoria or B. treatae. Overall, our results indicate that observed trade-offs in life history traits between the two gall former species are likely a result of independent adaptations in response to different environments as opposed to the amplified expression of within species intrinsic tradeoffs.
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Affiliation(s)
- Amy M Roush
- Department of BioSciences, Rice University, Houston, TX, 77005, USA
| | - Linyi Zhang
- Department of BioSciences, Rice University, Houston, TX, 77005, USA.
- Department of Biology, University of Toronto, Toronto, ON, M5S1A4, Canada.
- Department of Biological Sciences, George Washington University, Washington, DC, 20052, USA.
| | - Glen Ray Hood
- Department of Biological Sciences, Wayne State University, Detroit, MI, 48202, USA
| | - James R Ott
- Department of Biology, Population and Conservation Biology Program, Texas State University, San Marcos, TX, 78666, USA
| | - Scott P Egan
- Department of BioSciences, Rice University, Houston, TX, 77005, USA
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Bendall EE, Mattingly KM, Moehring AJ, Linnen CR. A Test of Haldane's Rule in Neodiprion Sawflies and Implications for the Evolution of Postzygotic Isolation in Haplodiploids. Am Nat 2023; 202:40-54. [PMID: 37384768 DOI: 10.1086/724820] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2023]
Abstract
AbstractHaldane's rule-a pattern in which hybrid sterility or inviability is observed in the heterogametic sex of an interspecific cross-is one of the most widely obeyed rules in nature. Because inheritance patterns are similar for sex chromosomes and haplodiploid genomes, Haldane's rule may apply to haplodiploid taxa, predicting that haploid male hybrids will evolve sterility or inviability before diploid female hybrids. However, there are several genetic and evolutionary mechanisms that may reduce the tendency of haplodiploids to obey Haldane's rule. Currently, there are insufficient data from haplodiploids to determine how frequently they adhere to Haldane's rule. To help fill this gap, we crossed a pair of haplodiploid hymenopteran species (Neodiprion lecontei and Neodiprion pinetum) and evaluated the viability and fertility of female and male hybrids. Despite considerable divergence, we found no evidence of reduced fertility in hybrids of either sex, consistent with the hypothesis that hybrid sterility evolves slowly in haplodiploids. For viability, we found a pattern opposite to that of Haldane's rule: hybrid females, but not males, had reduced viability. This reduction was most pronounced in one direction of the cross, possibly due to a cytoplasmic-nuclear incompatibility. We also found evidence of extrinsic postzygotic isolation in hybrids of both sexes, raising the possibility that this form or reproductive isolation tends to emerge early in speciation in host-specialized insects. Our work emphasizes the need for more studies on reproductive isolation in haplodiploids, which are abundant in nature but underrepresented in the speciation literature.
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Giertych MJ, Łukowski A, Karolewski P. Cynipid galls on oak leaves are resilient to leaf vein disruption. JOURNAL OF PLANT RESEARCH 2023:10.1007/s10265-023-01462-8. [PMID: 37133571 DOI: 10.1007/s10265-023-01462-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Accepted: 04/18/2023] [Indexed: 05/04/2023]
Abstract
Oaks serve as host plants for numerous insects, including those forming galls. Galls induced on oaks are completely dependent on leaf resources. Many other folivores damage veins of leaves, which may result in cutting galls off from sources of assimilates, nutrients and water. We hypothesised that the disruption of the continuity of leaf vascular tissues stops gall development, leading to the death of the larva. Leaves of sessile oak (Quercus petraea) with Cynips quercusfolii galls in the initial stage of development were marked. The diameter of the galls was measured, and the vein on which the gall was present was cut. Four experimental treatments were established: control - with no cutting, cutting the vein distal to the gall relative to the petiole, cutting the vein basal to the gall and cutting both sides. The average survival rate (live galls at the end of the experiment including healthy larvae, pupae or imagines inside) - was 28.9%. The rate varied depending on the treatment and was 13.6% in the treatment with the vein cut on both sides and about 30% in the remaining treatments. However, this difference was not statistically significant. The growth dynamics of galls are highly dependent on the experimental treatment. The largest galls grew in the control treatment, and the smallest galls were in the treatments with the veins cut on both sides. Unexpectedly, even cutting veins on both sides did not result in the immediate dieback of the galls. The results suggest that the galls are very strong nutrient and water sinks. The functions of the cut vein are likely taken over by other lower-order veins, allowing nourishment of the gall to complete larva development.
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Affiliation(s)
- Marian J Giertych
- Institute of Dendrology, Polish Academy of Sciences, Parkowa 5, Kórnik, 62-035, Poland.
- Faculty of Biological Sciences, University of Zielona Góra, Szafrana 1, Zielona Góra, 65-516, Poland.
| | - Adrian Łukowski
- Faculty of Forestry and Wood Technology, Poznań University of Life Sciences, Wojska Polskiego 71c, Poznań, 60-625, Poland
| | - Piotr Karolewski
- Institute of Dendrology, Polish Academy of Sciences, Parkowa 5, Kórnik, 62-035, Poland
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Zhang L, Chaturvedi S, Nice CC, Lucas LK, Gompert Z. Population genomic evidence of selection on structural variants in a natural hybrid zone. Mol Ecol 2023; 32:1497-1514. [PMID: 35398939 DOI: 10.1111/mec.16469] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 03/18/2022] [Accepted: 03/28/2022] [Indexed: 12/01/2022]
Abstract
Structural variants (SVs) can promote speciation by directly causing reproductive isolation or by suppressing recombination across large genomic regions. Whereas examples of each mechanism have been documented, systematic tests of the role of SVs in speciation are lacking. Here, we take advantage of long-read (Oxford nanopore) whole-genome sequencing and a hybrid zone between two Lycaeides butterfly taxa (L. melissa and Jackson Hole Lycaeides) to comprehensively evaluate genome-wide patterns of introgression for SVs and relate these patterns to hypotheses about speciation. We found >100,000 SVs segregating within or between the two hybridizing species. SVs and SNPs exhibited similar levels of genetic differentiation between species, with the exception of inversions, which were more differentiated. We detected credible variation in patterns of introgression among SV loci in the hybrid zone, with 562 of 1419 ancestry-informative SVs exhibiting genomic clines that deviated from null expectations based on genome-average ancestry. Overall, hybrids exhibited a directional shift towards Jackson Hole Lycaeides ancestry at SV loci, consistent with the hypothesis that these loci experienced more selection on average than SNP loci. Surprisingly, we found that deletions, rather than inversions, showed the highest skew towards excess ancestry from Jackson Hole Lycaeides. Excess Jackson Hole Lycaeides ancestry in hybrids was also especially pronounced for Z-linked SVs and inversions containing many genes. In conclusion, our results show that SVs are ubiquitous and suggest that SVs in general, but especially deletions, might disproportionately affect hybrid fitness and thus contribute to reproductive isolation.
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Affiliation(s)
- Linyi Zhang
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada.,Department of Biology, Utah State University, Logan, Utah, USA
| | - Samridhi Chaturvedi
- Department of Integrative Biology, University of California, Berkeley, California, USA
| | - Chris C Nice
- Department of Biology, Texas State University, San Marcos, Texas, USA
| | - Lauren K Lucas
- Department of Biology, Utah State University, Logan, Utah, USA
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Ward AKG, Bagley RK, Egan SP, Hood GR, Ott JR, Prior KM, Sheikh SI, Weinersmith KL, Zhang L, Zhang YM, Forbes AA. Speciation in Nearctic oak gall wasps is frequently correlated with changes in host plant, host organ, or both. Evolution 2022; 76:1849-1867. [PMID: 35819249 PMCID: PMC9541853 DOI: 10.1111/evo.14562] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Revised: 04/21/2022] [Accepted: 04/28/2022] [Indexed: 01/22/2023]
Abstract
Quantifying the frequency of shifts to new host plants within diverse clades of specialist herbivorous insects is critically important to understand whether and how host shifts contribute to the origin of species. Oak gall wasps (Hymenoptera: Cynipidae: Cynipini) comprise a tribe of ∼1000 species of phytophagous insects that induce gall formation on various organs of trees in the family Fagacae-primarily the oaks (genus Quercus; ∼435 sp.). The association of oak gall wasps with oaks is ancient (∼50 my), and most oak species are galled by one or more gall wasp species. Despite the diversity of both gall wasp species and their plant associations, previous phylogenetic work has not identified the strong signal of host plant shifting among oak gall wasps that has been found in other phytophagous insect systems. However, most emphasis has been on the Western Palearctic and not the Nearctic where both oaks and oak gall wasps are considerably more species rich. We collected 86 species of Nearctic oak gall wasps from most of the major clades of Nearctic oaks and sequenced >1000 Ultraconserved Elements (UCEs) and flanking sequences to infer wasp phylogenies. We assessed the relationships of Nearctic gall wasps to one another and, by leveraging previously published UCE data, to the Palearctic fauna. We then used phylogenies to infer historical patterns of shifts among host tree species and tree organs. Our results indicate that oak gall wasps have moved between the Palearctic and Nearctic at least four times, that some Palearctic wasp clades have their proximate origin in the Nearctic, and that gall wasps have shifted within and between oak tree sections, subsections, and organs considerably more often than previous data have suggested. Given that host shifts have been demonstrated to drive reproductive isolation between host-associated populations in other phytophagous insects, our analyses of Nearctic gall wasps suggest that host shifts are key drivers of speciation in this clade, especially in hotspots of oak diversity. Although formal assessment of this hypothesis requires further study, two putatively oligophagous gall wasp species in our dataset show signals of host-associated genetic differentiation unconfounded by geographic distance, suggestive of barriers to gene flow associated with the use of alternative host plants.
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Affiliation(s)
| | - Robin K. Bagley
- Department of BiologyUniversity of IowaIowa CityIowa52245,Department of Evolution, Ecology, and Organismal BiologyThe Ohio State UniversityLimaOhio45804
| | - Scott P. Egan
- Department of BioSciencesRice UniversityHoustonTexas77005
| | - Glen Ray Hood
- Department of BioSciencesRice UniversityHoustonTexas77005,Department of Biological ScienceWayne State UniversityDetroitMichigan48202
| | - James R. Ott
- Department of BiologyTexas State UniversitySan MarcosTexas78666
| | - Kirsten M. Prior
- Department of Biological SciencesBinghamton UniversityBinghamtonNew York13902
| | - Sofia I. Sheikh
- Department of BiologyUniversity of IowaIowa CityIowa52245,Department of Ecology and EvolutionUniversity of ChicagoChicagoIllinois60637
| | | | - Linyi Zhang
- Department of BioSciencesRice UniversityHoustonTexas77005,Department of Ecology and Evolutionary BiologyUniversity of TorontoTorontoONM5S 3B2Canada
| | - Y. Miles Zhang
- Systematic Entomology Laboratory, USDA‐ARSc/o National Museum of Natural HistoryWashingtonD.C.20560
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Zhang YM, Egan SP, Driscoe AL, Ott JR. One hundred and sixty years of taxonomic confusion resolved: Belonocnema (Hymenoptera: Cynipidae: Cynipini) gall wasps associated with live oaks in the USA. Zool J Linn Soc 2021. [DOI: 10.1093/zoolinnean/zlab001] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Abstract
Gall wasps (Hymenoptera: Cynipidae) in the genus Belonocnema induce galls on live oaks (Quercus series Virentes), forming multilocular root galls in the sexual generation and unilocular leaf galls in the asexual generation. Using morphological characters, host records, museum specimens, flight propensity and phylogenetic analysis of published cytochrome c oxidase subunit I (COI) and nuclear SNP data, we resolve the long-standing taxonomic confusion within Belonocnema and recognize three distinct species that are distributed throughout the southern and south-eastern USA: B. fossoria (rev. stat.), B. kinseyi (rev. stat.) and B. treatae, while B. quercusvirens is treated as species inquirenda. The presence of mitonuclear discordance results in the failure of a mitochondrial DNA barcode region to distinguish between B. fossoria and B. treatae, while recognizing B. kinseyi, despite the three species being clearly separated based on morphology and phylogenetic analysis of SNP data. We provide re-descriptions and an updated dichotomous key for both asexual and sexual generations of these widespread species. Finally, as Belonocnema has emerged as a model organism for ecological and evolutionary studies, we clarify the species examined in published studies to date.
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Affiliation(s)
- Y Miles Zhang
- Systematic Entomology Laboratory, USDA-ARS, c/o National Museum of Natural History, Washington, DC, USA
| | - Scott P Egan
- Department of Biosciences, Rice University, Houston, TX, USA
| | - Amanda L Driscoe
- Department of Biology, Population and Conservation Biology Program, Texas State University, San Marcos, TX, USA
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA
| | - James R Ott
- Department of Biology, Population and Conservation Biology Program, Texas State University, San Marcos, TX, USA
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