Data from: Recent northward range expansion promotes song evolution in a passerine bird, the Light-vented Bulbul

In common with human speech, song is culturally inherited in oscine passerine birds (‘songbirds’). Intraspecific divergence in birdsong, such as development of local dialects, might be an important early step in the speciation process. It is therefore vital to understand how songs diverge, especially in founding populations. The northward expansion of the Light-vented Bulbul Pycnonotus sinensis (J. F. Gmelin, 1789) into north China in the last 30 years provides an excellent opportunity to study birdsong evolution. We compared ~4400 songs from newly established northern populations with ~2900 songs from southern populations to evaluate song divergence after recent expansion. The total pool of syllables and especially song types was considerably smaller in the north than in the south, indicating ‘founder effects’ in the new population. The ancestral pattern of mosaic song dialects changed into a pattern of wide geographical sharing of a few song types and syllables, likely the result of fewer geographical barriers to ‘meme flow’, and the recent spread across a large area in the north. Our results suggest that song evolution and vocal trait shifts can arise rapidly after range expansion, and that in the Light-vented Bulbul ‘founder effects’, geographical isolation, and recent rapid expansions played important roles in the evolution of song dialects.

与人类语言类似，鸣禽雀形目鸟类（oscine passerine birds，下称‘鸣禽’）的鸣唱属于文化传承行为。鸟类鸣唱的种内分化——例如地方方言的形成——或许是物种形成进程中关键的早期环节。因此，阐明鸣唱分化的机制尤为关键，尤其针对奠基种群（founding populations）。过去30年间，白头鹎（Light-vented Bulbul，学名*Pycnonotus sinensis*，J. F. Gmelin, 1789）向北扩张至中国华北地区，为鸟类鸣唱演化研究提供了绝佳契机。本研究比对了新建立的北方种群的约4400条鸣唱样本与南方种群的约2900条鸣唱样本，以评估近期种群扩张后的鸣唱分化情况。北方种群的音节库乃至鸣唱类型总量均显著低于南方种群，表明新种群存在奠基者效应（founder effects）。原本的镶嵌式鸣唱方言祖先模式，转变为少数鸣唱类型与音节在广阔地理范围内共享的模式，这大概率源于‘模因流动（meme flow）’的地理屏障减少，以及北方种群近期在大范围区域内的扩散。本研究结果表明，种群范围扩张后，鸣唱演化与鸣唱性状变异可快速出现；同时，在白头鹎中，奠基者效应、地理隔离以及近期的快速种群扩张，在鸣唱方言的演化过程中发挥了重要作用。