Data from: Cultural isolation is greater than genetic isolation across an avian hybrid zone

Elucidating the relationship between genetic and cultural evolution is important in understanding speciation, as learned premating barriers might be involved in maintaining species differences. Here we test this relationship by examining a widely recognized premating barrier, bird song, in a hybrid zone between black-throated green (Setophaga virens) and Townsend's warblers (S. townsendi). We use song analysis, genomic techniques and playback experiments to characterize the cultural and genetic backgrounds of individuals in this region, expecting that if song is an important reproductive barrier between these species, there should be a strong relationship between song and genotype. We show that songs in the hybrid zone correspond to the distinctly different songs found in allopatry but that song and genotype are not tightly coupled in sympatry. Allopatric individuals responded only to local songs, indicating that individuals may have learned to respond to songs they commonly hear. We observed discordance between song and genotype clines; a narrower cline suggests that cultural selection on song is stronger than natural selection on genotype. These findings indicate that song is unlikely to play a role in reproductive isolation between these species, and we suggest that spatial variation in song may nonetheless be maintained by frequency-dependent cultural selection. This decoupling of genes and culture may contribute to hybridization in this region.

阐明遗传进化与文化进化之间的关联，对理解物种形成具有重要价值，因为习得的交配前障碍（premating barrier）可能参与维持物种间的差异。本研究以黑喉绿林莺（Setophaga virens）与汤森林莺（S. townsendi）的杂交带为研究对象，通过考察其中公认的交配前障碍——鸟类鸣唱，检验二者的关联。我们采用鸣唱分析、基因组技术与回放实验，对该区域内个体的文化背景与遗传背景进行表征，并提出预设：若鸣唱是这两个物种间的重要生殖障碍，则鸣唱与基因型之间应存在强关联。研究结果显示，杂交带内的鸣唱与异域分布（allopatry）种群中存在的两类截然不同的鸣唱类型相符，但同域分布（sympatry）种群内的鸣唱与基因型并未紧密耦合。异域种群个体仅对本地鸣唱产生响应，提示个体可能已学会对其常见鸣唱做出应答。我们还观察到鸣唱渐变群（cline）与基因型渐变群之间存在不一致：更窄的渐变群表明，对鸣唱的文化选择强度高于对基因型的自然选择强度。上述研究结果表明，鸣唱不太可能在这两个物种的生殖隔离中发挥作用，我们推测，鸣唱的空间变异仍可通过频率依赖型文化选择得以维持。这种基因与文化的解耦现象，可能促进了该区域内的杂交过程。