Data from: Dispersal to or from an African biodiversity hotspot?

Biodiversity hotspots are centers of endemism and thus contain many range-restricted species. In addition, within these hotspots are often widespread species that might have originated within a hotspot before dispersing to neighboring or distant regions. We test this hypothesis through a phylogeographic analysis of a miniature leaf litter frog, Arthroleptis xenodactyloides, that has a large distribution throughout the Eastern Arc, a biodiversity hotspot, and other regions in East Africa. Maximum likelihood and Bayesian estimates of the mitochondrial gene phylogeny are used as a proxy for understanding the evolutionary history of diversification and the historical relationships between populations. The north-south range of this species extends for approximately 1900 km; our sampling covers approximately 85% of this range. Using phylogenetic comparative methods, we estimate the region of origin and direction of dispersal within A. xenodactyloides. We compare contrasting hypotheses of latitudinal range expansion using bayes factors. The ancestral region of origin of A. xenodactyloides is reconstructed as having occurred within the Eastern Arc before dispersing southwards into the Southern Rift mountains, probably in the Pleistocene. The phylogeographic structure within this leaf litter frog is surprisingly similar to that of forest birds, revealing that similar geographic features might have had a driving role in diversification of these very dissimilar taxa. Latitudinal expansion occurred early in the evolutionary history of A. xenodactyloides and may indicate that physiological adaptation facilitated its wide geographic distribution.

生物多样性热点地区（biodiversity hotspot）是特有性中心，因此孕育了大量狭域分布物种。此外，这类热点区域内往往同时存在广布物种——这些物种可能起源于热点区域内部，随后扩散至周边或更远的区域。

我们以一种广泛分布于东弧（Eastern Arc）这一生物多样性热点地区及东非其他区域的小型枯落物蛙（Arthroleptis xenodactyloides）为研究对象，通过系统地理学分析检验上述假说。我们采用最大似然法与贝叶斯估计得到的线粒体基因系统发育结果，作为解析物种分化演化历史及种群间历史亲缘关系的替代指标。该物种的南北分布跨度约1900公里，我们的采样覆盖了其分布范围的85%左右。

通过系统发育比较分析方法，我们推断了A. xenodactyloides的起源区域与扩散方向，并利用贝叶斯因子对比了不同的纬度分布范围扩张假说。研究结果显示，A. xenodactyloides的祖先起源区域为东弧地区，随后于更新世时期向南扩散至南裂谷山脉。该枯落物蛙的系统地理学结构与森林鸟类的结构惊人相似，这表明相似的地理特征可能对这两类差异极大的类群的分化起到了驱动作用。纬度分布范围扩张发生在A. xenodactyloides演化历史的早期，这或许表明生理适应性助力其实现了广泛的地理分布。