Master genes or mass of genes? A view on the genomic architecture of speciation from amphibian hybrid zones


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Master genes or mass of genes? A view on the genomic architecture of speciation from amphibian hybrid zones
Proceedings of the National Academy of Sciences of the United States of America
Brelsford A., Jeffries D. L., Dufresnes C., Mazepa G., Suchan T., Canestrelli D., Nicieza A., Fumagalli L., Dubey S., Martinez-Solano I., Litvinchuk S. N., Vences M., Perrin N., Crochet P.-A.
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In Press
The genetic architecture of speciation, i.e. how intrinsic genomic incompatibilities promote reproductive isolation (RI) between diverging lineages, is one of the best-kept secrets of evolution. To directly assess whether incompatibilities arise in a limited set of large-effect speciation genes, or in a multitude of loci, we examined the geographic and genomic landscapes of introgression across the hybrid zones of 41 pairs of frog and toad lineages in the Western Palearctic region. As the divergence between lineages increases, phylogeographic transitions progressively become narrower, and larger parts of the genome resist introgression. This suggests that anuran speciation proceeds through a gradual accumulation of multiple barrier loci scattered across the genome, which ultimately deplete hybrid fitness by intrinsic post-zygotic isolation; behavioral isolation being achieved only at later stages. Moreover, these loci were disproportionately sex-linked in one group (Hyla), but not in others (Rana, Bufotes), implying that large X-effects are not necessarily a rule of speciation with undifferentiated sex chromosomes. The highly polygenic nature of RI and lack of hemizygous X/Z chromosomes could explain why the speciation clock ticks slower in amphibians compared to other vertebrates. Clock-like dynamics of speciation combined with the analytical focus on hybrid zones offer perspectives for more standardized practices of species delimitation.
cryptic species, Haldane’s rule, phylogeography, sex chromosomes, species delimitation
Create date
10/07/2021 21:45
Last modification date
25/07/2021 6:36
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