Extinction as a driver of avian latitudinal diversity gradients

The role of historical factors in driving latitudinal diversity gradients is poorly understood. Here we used an updated global phylogeny of terrestrial birds to test the role of three key historical factors – speciation, extinction and dispersal rates – in generating latitudinal diversity gradients for eight major clades. We fit a model that allows speciation, extinction and dispersal rates to differ, both with latitude and between the New and Old World. Our results consistently support extinction (all clades had lowest extinction where species richness was highest) as a key driver of species richness gradients across each of eight major clades. In contrast, speciation and dispersal rates showed no consistent latitudinal patterns across replicate bird clades, and thus are unlikely to represent general underlying drivers of latitudinal diversity gradients.历史因素在驱动纬度多样性梯度中的作用尚未被充分理解。本文利用更新后的全球陆栖鸟类系统发育树，针对八个主要分支，检验了三个关键历史因素——物种形成（speciation）、灭绝（extinction）和扩散速率（dispersal rates）——在生成纬度多样性梯度中的作用。我们拟合了一个模型，该模型允许物种形成、灭绝和扩散速率随纬度以及新旧大陆之间的差异而变化。结果一致支持灭绝（所有分支在物种丰富度最高的区域灭绝率最低）作为八个主要分支中每个分支物种丰富度梯度的关键驱动因素。相比之下，物种形成和扩散速率在重复鸟类分支中未显示出一致的纬度模式，因此不太可能代表纬度多样性梯度的普遍潜在驱动因素。