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（oscine passerine birds，即“鸣唱鸟类”）的鸣唱具有文化传承性。鸟类鸣唱的种内分化——例如地方方言的形成——或许是物种形成过程中关键的早期步骤。因此，阐明鸣唱如何发生分化，尤其是在奠基种群中，具有重要意义。近30年来，白头鹎（Light-vented Bulbul，学名*Pycnonotus sinensis*，J. F. Gmelin, 1789）向北扩张至中国北方地区，为研究鸟类鸣唱演化提供了绝佳契机。我们对比了新建立的北方种群的约4400首鸣唱与南方种群的约2900首鸣唱，以评估近期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少于南方种群，表明新种群存在“奠基者效应（founder effects）”。原本镶嵌状的鸣唱方言祖先模式，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，这可能源于“模因流（meme flow）”的地理屏障减少，加之该物种近期在北方大范围扩散。本研究结果显示，物种分布范围扩张后，鸣唱演化与鸣声特征改变可快速发生；同时，在白头鹎中，奠基者效应、地理隔离以及近期的快速扩张，在鸣唱方言的演化过程中扮演了重要角色。