Data from: The relative roles of cultural drift and acoustic adaptation in shaping syllable repertoires of island bird populations change with time since colonization

In birds, song divergence often precedes and facilitates divergence of other traits. We assessed the relative roles of cultural drift, innovation and acoustic adaptation in divergence of island bird dialects, using silvereyes (Zosterops lateralis). In recently colonized populations, syllable diversity was not significantly lower than source populations, shared syllables between populations decreased with increasing number of founder events and dialect variation displayed contributions from both habitat features and drift. The breadth of multivariate space occupied by recently colonized Z. l. lateralis populations was comparable to evolutionarily old forms that have diverged over thousands to hundreds of thousands of years. In evolutionarily old subspecies, syllable diversity was comparable to the mainland and the amount of variation in syllable composition explained by habitat features increased by two- to three-fold compared to recently colonized populations. Together these results suggest that cultural drift influences syllable repertoires in recently colonized populations, but innovation likely counters syllable loss from colonization. In evolutionarily older populations, the influence of acoustic adaptation increases, possibly favoring a high diversity of syllables. These results suggest that the relative importance of cultural drift and acoustic adaptation changes with time since colonization in island bird populations, highlighting the value of considering multiple mechanisms and timescale of divergence when investigating island song divergence.在鸟类类群中，鸣唱分化通常先于其他性状分化并推动其演化进程。本研究以银眼鹛（Zosterops lateralis）为研究模型，评估了文化漂变（cultural drift）、鸣唱创新与声学适应（acoustic adaptation）在海岛鸟类鸣唱方言分化中的相对作用。在新近定殖的种群中，其音节多样性（syllable diversity）与源种群无显著差异；种群间共享的音节数量随奠基者事件（founder events）发生次数的增加而减少，且鸣唱方言变异同时受到生境特征与文化漂变的影响。新近定殖的银眼鹛指名亚种（Z. l. lateralis）种群所占据的多元空间广度，可与历经数千至数十万年分化的演化古老类群相媲美。在演化古老的亚种中，其音节多样性与大陆种群相当，而生境特征对音节组成变异的解释度较新近定殖种群提升了2至3倍。综合上述结果可知，文化漂变会对新近定殖种群的鸣唱音节库产生影响，但鸣唱创新或可抵消定殖过程中出现的音节丢失现象。在演化年代更久远的种群中，声学适应的影响逐渐增强，或更青睐高多样性的鸣唱音节库。本研究结果表明，海岛鸟类种群的鸣唱分化中，文化漂变与声学适应的相对重要性会随定殖后时间的推移发生变化，这凸显了在探究海岛鸟类鸣唱分化时，综合考量多种演化机制与分化时间尺度的重要价值。