Data from: Genomic islands of differentiation in two songbird species reveal candidate genes for hybrid female sterility

Hybrid sterility is a common first step in the evolution of postzygotic
reproductive isolation. According to Haldane’s Rule it affects
predominantly the heterogametic sex. While the genetic basis of hybrid
male sterility in organisms with heterogametic males has been studied for
decades, the genetic basis of hybrid female sterility in organisms with
heterogametic females has received much less attention. We investigated
the genetic basis of reproductive isolation in two closely related avian
species, the Common Nightingale (Luscinia megarhynchos) and the Thrush
Nightingale (L. luscinia), that hybridize in a secondary contact zone and
produce viable hybrid progeny. In accordance with Haldane’s Rule, hybrid
females are sterile, while hybrid males are fertile, allowing gene flow to
occur between the species. Using transcriptomic data from multiple
individuals of both nightingale species we identified genomic islands of
high differentiation (FST) and of high divergence (Dxy), and we analyzed
gene content and patterns of molecular evolution within these islands.
Interestingly, we found that these islands were enriched for genes related
to female meiosis and metabolism. The islands of high differentiation and
divergence were also characterized by higher levels of linkage
disequilibrium than the rest of the genome in both species indicating that
they might be situated in genomic regions of low recombination. This study
provides one of the first insights into genetic basis of hybrid female
sterility in organisms with heterogametic females.