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.

与人类语言相仿，鸣禽亚目（oscine passerine，俗称鸣禽）的鸣唱属于文化传承的行为。鸣唱的种内分化——例如地方方言的形成——或许是物种形成过程中关键的早期步骤。因此，阐明鸣唱的分化机制至关重要，尤其是在奠基种群（founding populations）中。过去30年间，白头鹎（Light-vented Bulbul，学名Pycnonotus sinensis，J. F. Gmelin, 1789）向北扩散至中国北方，为研究鸟类鸣唱演化提供了绝佳的研究契机。本研究对比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，以评估近期扩散后的鸣唱分化情况。北方种群的音节库乃至鸣唱类型总数量均显著低于南方种群，表明新种群存在奠基者效应（founder effects）。祖先种群的镶嵌式鸣唱方言分布模式，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，这可能源于北方地区地理屏障对模因流（meme flow）的阻碍减弱，加之近期的大范围扩散事件。本研究结果表明，种群扩散后鸣唱演化与鸣唱性状的改变可快速发生；同时，在白头鹎中，奠基者效应、地理隔离以及近期的快速扩散，均在鸣唱方言的演化过程中发挥了重要作用。