Machac Antonin, Graham Catherine H
Am Nat. 2017 Jan;189(1):E1-E13. doi: 10.1086/689398. Epub 2016 Nov 9.
The effects of regional diversity on diversification remain controversial. The classic hypothesis that diversification decelerates as regional diversity increases has been recently revived. Yet, there is little geographic evidence for slower diversification across regions of high diversity, and diversity is often thought to promote diversification through its effects on ecological divergence and speciation. Here, we use the newest phylogeny for mammals (4,990 species) and two different methods to test the effects of regional diversity on diversification. We find that regions of high diversity are dominated by expanding clades that are far from their estimated carrying capacities. Regions of low diversity host clades that are small and mostly saturated. These results were supported across mammals and their six largest orders. They were corroborated by the two methods when controlling for clade relatedness, clade nestedness, and clade size. Together, these results reject the hypothesis that high geographic concentration of mammals effectively suppresses their further diversification. Instead, highly diverse regions (especially the tropics) seem to act as the engine of mammalian richness.
区域多样性对物种分化的影响仍存在争议。经典假说认为，随着区域多样性的增加，物种分化速度会减缓，这一假说最近又被重新提起。然而，几乎没有地理证据表明在高多样性区域物种分化速度会变慢，而且人们通常认为多样性通过对生态趋异和物种形成的影响来促进物种分化。在此，我们使用最新的哺乳动物系统发育树（4990个物种）和两种不同方法来测试区域多样性对物种分化的影响。我们发现，高多样性区域主要由远离其估计承载能力的扩张分支所主导。低多样性区域容纳的是小型且大多饱和的分支。这些结果在整个哺乳动物及其六个最大目类中均得到支持。在控制分支亲缘关系、分支嵌套性和分支大小时，这两种方法也证实了这些结果。总之，这些结果否定了哺乳动物的高地理集中度会有效抑制其进一步物种分化的假说。相反，高度多样化的区域（尤其是热带地区）似乎是哺乳动物丰富度的引擎。
