Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada.
Proc Biol Sci. 2011 Jun 7;278(1712):1713-20. doi: 10.1098/rspb.2010.2037. Epub 2010 Nov 10.
We ask whether rates of evolution in traits important for reproductive isolation vary across a latitudinal gradient, by quantifying evolutionary rates of two traits important for pre-mating isolation-avian syllable diversity and song length. We analyse over 2500 songs from 116 pairs of closely related New World passerine bird taxa to show that evolutionary rates for the two main groups of passerines-oscines and suboscines-doubled with latitude in both groups for song length. For syllable diversity, oscines (who transmit song culturally) evolved more than 20 times faster at high latitudes than in low latitudes, whereas suboscines (whose songs are innate in most species and who possess very simple song with few syllable types) show no clear latitudinal gradient in rate. Evolutionary rates in oscines and suboscines were similar at tropical latitudes for syllable complexity as well as for song length. These results suggest that evolutionary rates in traits important to reproductive isolation and speciation are influenced by latitude and have been fastest, not in the tropics where species diversity is highest, but towards the poles.
我们通过量化对交配前隔离至关重要的两个特征——鸟类音节多样性和鸣唱长度的进化速率，来探讨在纬度梯度上，与生殖隔离相关的特征的进化速率是否存在差异。我们分析了来自 116 对近缘新世界雀形目鸟类的 2500 多首鸣唱，结果表明，在两个雀形目群体——鸣禽和亚鸣禽中，鸣唱长度的进化速率随着纬度的增加而翻倍。对于音节多样性，鸣禽（通过文化传播鸣唱）在高纬度地区的进化速度比在低纬度地区快 20 多倍，而亚鸣禽（其鸣唱在大多数物种中是天生的，并且具有很少音节类型的非常简单的鸣唱）在速率上没有明显的纬度梯度。在热带纬度地区，鸣禽和亚鸣禽的音节复杂性以及鸣唱长度的进化速率相似。这些结果表明，对生殖隔离和物种形成至关重要的特征的进化速率受到纬度的影响，并且最快的不是物种多样性最高的热带地区，而是两极地区。
