Kozak Kenneth H, Wiens John J
Bell Museum of Natural History and Department of Fisheries, Wildlife, and Conservation Biology University of Minnesota St. Paul Minnesota 55108.
Department of Ecology and Evolution University of Arizona Tucson Arizona 85721.
Ecol Evol. 2016 Jul 26;6(16):5940-9. doi: 10.1002/ece3.2301. eCollection 2016 Aug.
A major goal of evolutionary biology and ecology is to understand why species richness varies among clades. Previous studies have suggested that variation in richness among clades might be related to variation in rates of morphological evolution among clades (e.g., body size and shape). Other studies have suggested that richness patterns might be related to variation in rates of climatic-niche evolution. However, few studies, if any, have tested the relative importance of these variables in explaining patterns of richness among clades. Here, we test their relative importance among major clades of Plethodontidae, the most species-rich family of salamanders. Earlier studies have suggested that climatic-niche evolution explains patterns of diversification among plethodontid clades, whereas rates of morphological evolution do not. A subsequent study stated that rates of morphological evolution instead explained patterns of species richness among plethodontid clades (along with "ecological limits" on richness of clades, leading to saturation of clades with species, given limited resources). However, they did not consider climatic-niche evolution. Using phylogenetic multiple regression, we show that rates of climatic-niche evolution explain most variation in richness among plethodontid clades, whereas rates of morphological evolution do not. We find little evidence that ecological limits explain patterns of richness among plethodontid clades. We also test whether rates of morphological and climatic-niche evolution are correlated, and find that they are not. Overall, our results help explain richness patterns in a major amphibian group and provide possibly the first test of the relative importance of climatic niches and morphological evolution in explaining diversity patterns.
进化生物学和生态学的一个主要目标是理解为什么物种丰富度在不同的进化枝中会有所不同。先前的研究表明，进化枝间丰富度的差异可能与进化枝间形态进化速率的差异有关（例如，体型和形状）。其他研究则表明，丰富度模式可能与气候生态位进化速率的差异有关。然而，几乎没有研究（如果有的话）检验过这些变量在解释进化枝间丰富度模式方面的相对重要性。在这里，我们检验它们在无肺螈科主要进化枝中的相对重要性，无肺螈科是蝾螈中物种最丰富的科。早期研究表明，气候生态位进化解释了无肺螈科进化枝间的多样化模式，而形态进化速率则不然。随后的一项研究指出，形态进化速率反而解释了无肺螈科进化枝间的物种丰富度模式（以及进化枝丰富度的“生态限制”，即在资源有限的情况下，导致进化枝物种饱和）。然而，他们没有考虑气候生态位进化。通过系统发育多元回归，我们表明气候生态位进化速率解释了无肺螈科进化枝间丰富度的大部分变异，而形态进化速率则不然。我们几乎没有发现证据表明生态限制解释了无肺螈科进化枝间的丰富度模式。我们还检验了形态和气候生态位进化速率是否相关，发现它们不相关。总体而言，我们的结果有助于解释一个主要两栖动物类群的丰富度模式，并可能首次检验了气候生态位和形态进化在解释多样性模式方面的相对重要性。
