Determinants of genetic diversity and species richness of North American amphibians

Aim: Ecological limits on population sizes and the number of species a region can sustain are thought to simultaneously produce spatial patterns in population genetic diversity and species richness due to the effects of random drift operating in parallel across population and community levels. Here, we test the extent to which resource-based environmental limits jointly determine these patterns of biodiversity in amphibians.

Location: North America.

Taxon: Amphibians.

Methods: We repurposed open, raw microsatellite data from 19 species sampled at 554 sites in North America and mapped nuclear genetic diversity at the continental scale. We then tested whether ecological limits defined by resource availability and environmental heterogeneity could simultaneously shape biogeographic patterns in genetic diversity and species richness with structural equation modeling.

Results: Spatial patterns of population genetic diversity run opposite patterns of species richness and genetic differentiation. However, while measures of resource availability and niche heterogeneity predict 89% of the variation in species richness, these landscape metrics were poor predictors of genetic diversity.

Main conclusions: Although heterogeneity appears to be an important driver of genetic and species biodiversity patterns in amphibians, variation in genetic diversity both within and across species makes it difficult to infer general processes producing spatial patterns of amphibian genetic diversity. This result differs from those found in endotherms and may be due to the considerable life history variation found across amphibians.

研究目的：学界普遍认为，由于随机遗传漂变在种群与群落两个层面并行发挥作用，区域可承载的种群规模与物种数量所受的生态限制，会同时催生种群遗传多样性与物种丰富度的空间分布格局。本研究旨在验证：基于资源的环境限制是否能够共同决定两栖类（Amphibians）生物多样性的上述两类分布模式。
研究区域：北美洲。
研究类群：两栖类（Amphibians）。
研究方法：本研究复用了北美洲554个采样点、19个物种种群的公开原始微卫星（microsatellite）数据，在大陆尺度上绘制了核遗传多样性的空间分布图谱。随后，采用结构方程模型（structural equation modeling），检验由资源可获得性与环境异质性所定义的生态限制，是否可同时塑造遗传多样性与物种丰富度的生物地理分布格局。
研究结果：种群遗传多样性的空间分布格局与物种丰富度、遗传分化的格局呈相反趋势。尽管资源可获得性与生态位异质性的指标可解释89%的物种丰富度变异，但此类景观指标对遗传多样性的预测能力却极为有限。
主要结论：尽管环境异质性似乎是两栖类遗传与物种生物多样性分布格局的重要驱动因素，但物种种内与种间的遗传多样性变异，使得我们难以推断塑造两栖类遗传多样性空间分布的通用过程。这一结果与恒温动物（endotherms）中的相关研究结论存在差异，其成因可能在于两栖类类群间存在显著的生活史特征差异。