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（tree of life）各分支的物种分化（species diversification）与表型演化（phenotypic evolution）的节奏与模式广泛存在差异，但学界对这两类过程间的关联仍知之甚少。过往针对表型演化速率与物种分化速率间关联的检验，均假定物种丰富度（species richness）随时间持续增长。若该假定不成立，则基于系统发育（phylogenetic）的简单净分化速率（net diversification rate）估计值，或与影响支系（clades）间物种丰富度分布的演化过程毫无关联。本研究证实，无肺螈科（Plethodontidae）蝾螈各支系间的物种丰富度差异，不太可能由简单的时间依赖性过程所导致，这使得我们对表型演化速率与物种分化速率间的关联得出了截然不同的结论。体型与形态演化的形态学演化速率，均与支系物种丰富度呈显著相关，但与那些假定演化速率随时间恒定的简单净分化速率估计值并无关联。这种物种分化与表型演化间的耦合关系，与“形态性状演化速率较高的支系，其物种分化程度可能高于演化速率较低的支系”这一假说相符。本研究结果表明，关于多样性调控内在过程的假定，对解读宏观演化（macroevolutionary）格局具有重要影响。