Data from: Rates of morphological evolution are correlated with species richness in salamanders

The tempo and mode of species diversification and phenotypic evolution vary widely across the tree of life, yet the relationship between these processes is poorly known. Previous tests of the relationship between rates of phenotypic evolution and rates of species diversification have assumed that species richness increases continuously through time. If this assumption is violated, simple phylogenetic estimates of net diversification rate may bear no relationship to processes that influence the distribution of species richness among clades. Here we demonstrate that the variation in species richness among plethodontid salamander clades is unlikely to have resulted from simple time-dependent processes, leading to fundamentally different conclusions about the relationship between rates of phenotypic evolution and species diversification. Morphological evolutionary rates of both size and shape evolution are correlated with clade species richness, but are uncorrelated with simple estimators of net diversification that assume constancy of rates through time. This coupling between species diversification and phenotypic evolution is consistent with the hypothesis that clades with high rates of morphological trait evolution may diversify more than clades with low rates. Our results indicate that assumptions about underlying processes of diversity regulation have important consequences for interpreting macroevolutionary patterns.

生命之树中，物种分化（species diversification）与表型进化（phenotypic evolution）的节奏与模式差异悬殊，但二者间的关联机制仍尚不明确。过往针对表型进化速率与物种分化速率之间关联的检验研究，均默认物种丰富度随时间持续增长。若该假设不成立，则净分化速率（net diversification rate）的简易系统发育（phylogenetic）估计值，或许与影响演化支（clades）间物种丰富度分布的过程毫无关联。本研究证实，无肺螈科（Plethodontidae）蝾螈各演化支的物种丰富度差异，不太可能由单纯的时间依赖型过程所致，这使得我们对表型进化速率与物种分化速率间的关联得出了截然不同的结论。体型与形状进化的形态进化速率均与演化支物种丰富度呈显著相关，但与假定进化速率恒定的净分化速率简易估计量并无关联。这种物种分化与表型进化之间的耦合现象，契合如下假说：形态性状进化速率较高的演化支，其物种分化程度或许高于进化速率较低的演化支。本研究结果表明，有关多样性调控底层过程的假设，对解读宏进化（macroevolutionary）模式具有重要影响。