Nwankwo Emmanuel C, Pallari Chryso Th, Hadjioannou Louis, Ioannou Andreas, Mulwa Ronald K, Kirschel Alexander N G
Department of Biological Sciences University of Cyprus Nicosia Cyprus.
Ornithology Section, Zoology Department National Museums of Kenya Nairobi Kenya.
Ecol Evol. 2017 Dec 5;8(1):716-731. doi: 10.1002/ece3.3673. eCollection 2018 Jan.
The criteria for species delimitation in birds have long been debated, and several recent studies have proposed new methods for such delimitation. On one side, there is a large consensus of investigators who believe that the only evidence that can be used to delimit species is molecular phylogenetics, and with increasing numbers of markers to gain better support, whereas on the other, there are investigators adopting alternative approaches based largely on phenotypic differences, including in morphology and communication signals. Yet, these methods have little to say about rapid differentiation in specific traits shown to be important in reproductive isolation. Here, we examine variation in phenotypic (morphology, plumage, and song) and genotypic (mitochondrial and nuclear DNA) traits among populations of yellow-rumped tinkerbird in East Africa. Strikingly, song divergence between the subspecies from Kenya and Zanzibar and from Tanzania is discordant with genetic distance, having occurred over a short time frame, and playback experiments show that adjacent populations of and do not recognize one another's songs. While such rapid divergence might suggest a founder effect following invasion of Zanzibar, molecular evidence suggests otherwise, with insular nested within mainland . Populations from the Eastern Arc Mountains are genetically more distant, yet share the same song with from Coastal Tanzania and Southern Africa, suggesting they would interbreed. We believe investigators ought to examine potentially rapid divergence in traits important in species recognition and sexual selection when delimiting species, rather than relying entirely on arbitrary quantitative characters or molecular markers.
鸟类物种界定的标准长期以来一直存在争议，最近的几项研究提出了新的界定方法。一方面，有很大一部分研究者达成共识，认为可用于界定物种的唯一证据是分子系统发育学，并且随着标记数量的增加以获得更好的支持；而另一方面，有研究者采用主要基于表型差异的替代方法，包括形态学和通讯信号方面的差异。然而，这些方法对于在生殖隔离中显示出重要性的特定性状的快速分化几乎没有涉及。在这里，我们研究了东非黄腰细嘴雀种群之间表型（形态、羽毛和鸣声）和基因型（线粒体和核DNA）性状的变异。令人惊讶的是，来自肯尼亚和桑给巴尔的亚种与来自坦桑尼亚的亚种之间的鸣声差异与遗传距离不一致，这种差异在短时间内就出现了，回放实验表明相邻的和种群不识别彼此的鸣声。虽然这种快速分化可能表明桑给巴尔被入侵后出现了奠基者效应，但分子证据却表明情况并非如此，岛屿种群嵌套在大陆种群之中。东弧山脉的种群在基因上距离更远，但与来自坦桑尼亚沿海和南部非洲的种群共享相同的鸣声，这表明它们可能会杂交。我们认为，研究者在界定物种时，应该研究在物种识别和性选择中重要的性状可能出现的快速分化，而不是完全依赖任意的定量特征或分子标记。
