The Past and Future of Experimental Speciation

White, Nathan J.; Snook, Rhonda R.; Eyres, Isobel

doi:10.1016/j.tree.2019.08.009

Cited by 39 publications

(29 citation statements)

References 96 publications

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“…However, a disadvantage is that the time scale over which divergence can be studied is typically much shorter than evolutionary time-scales in nature. Studies of experimental evolution and speciation are in their infancy, and general conclusions are, as yet, difficult to draw (White et al, 2020). Enforcing monogamy in otherwise polyandrous species will lead to both changes in the intensity of sexual selection and the balance of sexual conflict, as it effectively eliminates sexual selection and sexually antagonistic selection.…”

Section: Introductionmentioning

confidence: 99%

Experimental evolution supports signatures of sexual selection in genomic divergence

Wiberg

Veltsos

Snook

et al. 2020

Preprint

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Comparative genomics has contributed to the growing evidence that sexual selection is an important component of evolutionary divergence and speciation. Divergence by sexual selection is implicated in faster rates of divergence of the X chromosome and of genes thought to underlie sexually selected traits, including genes that are sex-biased in expression. However, accurately inferring the relative importance of complex and interacting forms of natural selection, demography and neutral processes which occurred in the evolutionary past is challenging. Experimental evolution provides an opportunity to apply controlled treatments for multiple generations and examine the consequences for genomic divergence. Here we altered sexual selection intensity, elevating sexual selection in polyandrous lines and eliminating it in monogamous lines, and examined patterns of divergence in the genome of Drosophila pseudoobscura after more than 160 generations of experimental evolution. Divergence is not uniform across the genome but concentrated in "islands", many of which contain candidate genes implicated in mating behaviours and other sexually selected phenotypes. These are more often seen on the X chromosome, which overall shows divergence above neutral expectations. There are also characteristic signatures of selection seen in these regions, with lower diversity and greater Fst on the X chromosome than the autosomes, and differences in diversity on the autosomes between selection regimes. Reduced Tajima's D implies that selective sweeps have occurred within the divergent regions, despite considerable recombination. These changes are associated with both differential gene expression between the lines and sex-biased gene expression within the lines. Our results are very similar to those thought to implicate sexual selection in divergence in natural populations, and hence provide experimental confirmation of the likely role of sexual selection in driving such types of genetic divergence, but also illustrate how variable outcomes can be for different genomic regions.

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Section: Introductionmentioning

confidence: 99%

Experimental evolution supports signatures of sexual selection in genomic divergence

Wiberg

Veltsos

Snook

et al. 2020

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…Studies of experimental evolution and speciation are in their infancy, most have studied phenotypic rather than genomic divergence, and general conclusions are, as yet, difficult to draw (White et al. 2020). Enforcing monogamy in otherwise polyandrous species will lead to both changes in the intensity of sexual selection and the balance of sexual conflict, as it effectively eliminates sexual selection and sexually antagonistic selection.…”

mentioning

confidence: 99%

Experimental evolution supports signatures of sexual selection in genomic divergence

et al. 2021

Self Cite

View full text Add to dashboard Cite

Comparative genomics has contributed to the growing evidence that sexual selection is an important component of evolutionary divergence and speciation. Divergence by sexual selection is implicated in faster rates of divergence of the X chromosome and of genes thought to underlie sexually selected traits, including genes that are sex biased in expression. However, accurately inferring the relative importance of complex and interacting forms of natural selection, demography, and neutral processes that occurred in the evolutionary past is challenging. Experimental evolution provides an opportunity to apply controlled treatments for multiple generations and examine the consequent genomic divergence. Here, we altered sexual selection intensity, elevating sexual selection in polyandrous lines and eliminating it in monogamous lines, and examined patterns of allele frequency divergence in the genome of Drosophila pseudoobscura after more than 160 generations of experimental evolution. Divergence is not uniform across the genome but concentrated in “islands,” many of which contain candidate genes implicated in mating behaviors and other sexually selected phenotypes. These are more often seen on the X chromosome, which also shows greater divergence in FST than neutral expectations. There are characteristic signatures of selection seen in these regions, with lower diversity on the X chromosome than the autosomes, and differences in diversity on the autosomes between selection regimes. Reduced Tajima's D within some of the divergent regions may imply that selective sweeps have occurred, despite considerable recombination. These changes are associated with both differential gene expression between the lines and sex‐biased gene expression within the lines. Our results are very similar to those thought to implicate sexual selection in divergence between species and natural populations, and hence provide experimental support for the likely role of sexual selection in driving such types of genetic divergence, but also illustrate how variable outcomes can be for different genomic regions.

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“…To date, the majority of studies analysing the genetic basis of speciation have involved retrospective approaches, whereby the mechanisms of speciation were reconstructed retroactively after the speciation process was completed (Via, 2009). Early stages of genomic differentiation provide rare windows into early barriers to gene flow that precede speciation, and represent excellent opportunities to detect genomic elements that may be under divergent selection, before these are overwritten as the process evolves (White et al, 2020). The analysis of partially reproductively isolated morphotypes can contribute to disentangle genetic changes contributing to reproductive isolation from genetic differences between species that accumulate after speciation is complete.…”

Section: Introductionmentioning

confidence: 99%

Genomic landscape of geographically structured colour polymorphism in a temperate marine fish

et al. 2021

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The study of phenotypic variation patterns among populations is fundamental to elucidate the drivers of evolutionary processes. Empirical evidence that supports ongoing genetic divergence associated with phenotypic variation remains very limited for marine species where larval dispersal is a common homogenizing force. We present a genome‐wide analysis of a marine fish, Labrus bergylta, comprising 144 samples distributed from Norway to Spain, a large geographical area that harbours a gradient of phenotypic differentiation. We analysed 39,602 biallelic single nucleotide polymorphisms and found a clear latitudinal gradient of genomic differentiation strongly correlated with the variation in phenotypic morph frequencies observed across the North Atlantic. We also detected a strong association between the latitude and the number of loci that appear to be under divergent selection, which increased with differences in coloration but not with overall genetic differentiation. Our results demonstrate that strong reproductive isolation is occurring between sympatric colour morphs of L. bergylta found at the southern areas and provide important new insights into the genomic changes shaping early stages of differentiation that might precede speciation with gene flow.

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The Past and Future of Experimental Speciation

Cited by 39 publications

References 96 publications

Experimental evolution supports signatures of sexual selection in genomic divergence

Experimental evolution supports signatures of sexual selection in genomic divergence

Experimental evolution supports signatures of sexual selection in genomic divergence

Genomic landscape of geographically structured colour polymorphism in a temperate marine fish

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