Z‐chromosome outliers as diagnostic markers to discriminate Mallard and Chinese Spot‐billed Duck (Anatidae). (28th April 2022) - Kulikova, Irina V.
Abstract: Closely related bird species often exhibit elevated differentiation in the Z‐chromosome. Genetic differentiation is repeatedly found in so‐called 'islands of differentiation' that might contain loci under selection that contribute to reproductive isolation. Using double‐digest restriction‐associated DNA sequencing (ddRAD‐seq), we examined genomic divergence of Mallard ( Anas platyrhynchos ) and Chinese Spot‐billed Duck ( A. zonorhyncha ), two closely related species of ducks that occasionally hybridize. The taxa were distinguishable based on overall ddRAD‐seq allele frequency differences. However, differentiation on the Z‐chromosome was about 4.5 times greater than observed for autosomal DNA and included three fixed differences in SNPs. These SNPs are the first species‐specific molecular markers revealed among mallard group species. The causes of elevated Z‐chromosome divergence are discussed, including the possibility that Z‐linked loci are resistant to introgression and potentially linked to phenotypic differences between the species.