Saetre Glenn-Peter, Borge Thomas, Lindroos Katarina, Haavie Jon, Sheldon Ben C, Primmer Craig, Syvänen Ann-Christine
Department of Evolutionary Biology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18d, SE-752 36 Uppsala, Sweden.
Proc Biol Sci. 2003 Jan 7;270(1510):53-9. doi: 10.1098/rspb.2002.2204.
Speciation is the combination of evolutionary processes that leads to the reproductive isolation of different populations. We investigate the significance of sex-chromosome evolution on the development of post- and prezygotic isolation in two naturally hybridizing Ficedula flycatcher species. Applying a tag-array-based mini-sequencing assay to genotype single nucleotide polymorphisms (SNPs) and interspecific substitutions, we demonstrate rather extensive hybridization and backcrossing in sympatry. However, gene flow across the partial postzygotic barrier (introgression) is almost exclusively restricted to autosomal loci, suggesting strong selection against introgression of sex-linked genes. In addition to this partial postzygotic barrier, character displacement of male plumage characteristics has previously been shown to reinforce prezygotic isolation in these birds. We show that male plumage traits involved in reinforcing prezygotic isolation are sex linked. These results suggest a major role of sex-chromosome evolution in mediating post- and prezygotic barriers to gene flow and point to a causal link in the development of the two forms of reproductive isolation.
物种形成是导致不同种群生殖隔离的进化过程的组合。我们研究了性染色体进化对两种自然杂交的姬鹟物种中合子后隔离和合子前隔离发展的重要性。通过应用基于标签阵列的微测序分析来对单核苷酸多态性（SNP）和种间替代进行基因分型，我们证明了在同域中存在相当广泛的杂交和回交现象。然而，跨越部分合子后屏障（基因渗入）的基因流几乎完全局限于常染色体位点，这表明对性连锁基因的渗入存在强烈选择。除了这种部分合子后屏障外，此前已表明雄性羽毛特征的特征取代会加强这些鸟类的合子前隔离。我们表明，参与加强合子前隔离的雄性羽毛性状是性连锁的。这些结果表明性染色体进化在介导基因流的合子后和合子前屏障中起主要作用，并指出了两种生殖隔离形式发展中的因果联系。
