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The guppy Y chromosome has been considered a model system for the evolution of suppressed recombination between sex chromosomes, and it has been proposed that complete sex-linkage has evolved across about 3 Mb surrounding this fish’s sex-determining locus, followed by recombination suppression across a further 7 Mb of the 23 Mb XY pair, forming younger “evolutionary strata”. Sequences of the guppy genome show that Y is very similar to the X chromosome. Knowing which parts of the Y are completely non-recombining, and whether there is indeed a large completely non-recombining region, are important for understanding its evolution. Here, we describe analyses of PoolSeq data in samples from within multiple natural populations from Trinidad, yielding new results that support previous evidence for occasional recombination between the guppy Y and X. We detect recent demographic changes, notably that downstream populations have higher synonymous site diversity than upstream ones and other expected signals of bottlenecks). We detect evidence of associations between sequence variants and the sex-determining locus, rather than divergence under a complete lack of recombination. Although recombination is infrequent, it is frequent enough that associations with SNPs can suggest the region in which the sex-determining locus must be located. Diversity is elevated across a physically large region of the sex chromosome, conforming to predictions for a genome region with infrequent recombination that carries one or more sexually antagonistic polymorphisms. However, no consistently male-specific variants were found, supporting the suggestion that any completely sex-linked region may be very small.
|Number of pages||14|
|Early online date||25 Aug 2022|
|Publication status||Published - 1 Nov 2022|
- linkage disequilibrium
- genome assembly
- partial sex linkage
- sexual antagonism
- balancing selection
- evolutionary strata
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GUPPYSEX: Evolutionary genetics of guppy sex chromosomes
1/08/16 → 31/07/22