Department of Biology, University of Miami, Coral Gables, Florida, 33146, USA.
Department of Biology, University of Rochester, Rochester, New York, 14627, USA.
Mol Ecol. 2023 Jul;32(13):3586-3604. doi: 10.1111/mec.16938. Epub 2023 Apr 4.
After establishing secondary contact, recently diverged populations may remain reproductively isolated or may hybridize to a varying extent depending on factors such as hybrid fitness and the strength of assortative mating. Here, we used genomic and phenotypic data from three independent contact zones between subspecies of the variable seedeater (Sporophila corvina) to examine how coloration and genetic divergence shape patterns of hybridization. We found that differences in plumage coloration are probably maintained by divergent selection across contact zones; however, the degree of plumage differentiation does not match overall patterns of hybridization. Across two parallel contact zones between populations with divergent phenotypes (entirely black vs. pied plumage), populations hybridized extensively across one contact zone but not the other, suggesting that plumage divergence is not sufficient to maintain reproductive isolation. Where subspecies hybridized, hybrid zones were wide and formed by later-generation hybrids, suggesting frequent reproduction and high survivorship for hybrid individuals. Moreover, contemporary gene flow has played an important role in shaping patterns of genetic structure between populations. Replicated contact zones between hybridizing taxa offer a unique opportunity to explore how different factors interact to shape patterns of hybridization. Overall, our results demonstrate that divergence in plumage coloration is important in reducing gene flow but insufficient in maintaining reproductive isolation in this clade, and that other factors such as divergence in song and time since secondary contact may also play an important role in driving patterns of reduced hybridization and gene flow.
在建立二次接触后，最近分化的种群可能仍然保持生殖隔离，或者根据杂种适合度和交配选择性等因素在不同程度上杂交。在这里，我们使用了来自三个独立的可变食籽雀亚种间接触区的基因组和表型数据，以研究颜色和遗传分化如何影响杂交模式。我们发现，羽色差异可能是通过接触区之间的分歧选择来维持的；然而，羽色分化的程度与杂交的总体模式不匹配。在两个具有不同表型的种群之间的两个平行接触区中（完全黑色与花斑羽毛），一个接触区的种群广泛杂交，但另一个接触区没有杂交，这表明羽色分化不足以维持生殖隔离。在亚种杂交的地方，杂交区很宽，由后代杂种形成，这表明杂种个体的繁殖和生存能力较高。此外，现代基因流在塑造种群间遗传结构模式方面发挥了重要作用。杂交分类群之间的重复接触区为探索不同因素如何相互作用以塑造杂交模式提供了独特的机会。总体而言，我们的研究结果表明，羽色分化在减少基因流方面很重要，但在维持这个分支的生殖隔离方面是不够的，而其他因素，如歌声和二次接触以来的时间差异，也可能在驱动杂交和基因流减少的模式中发挥重要作用。
