Data from: Glaciations, gradients, and geography: multiple drivers of diversification of bush frogs in the Western Ghats Escarpment

The historical processes underlying high diversity in tropical biodiversity hotspots like the Western Ghats of Peninsular India remain poorly understood. We sampled bush frogs on 13 massifs across the Western Ghats Escarpment and examined the relative influence of Quaternary glaciations, ecological gradients and geological processes on the spatial patterns of lineage and clade diversification. The results reveal a large in situ radiation (more than 60 lineages), exhibiting geographical structure and clade-level endemism, with two deeply divergent sister clades, North and South, highlighting the biogeographic significance of an ancient valley, the Palghat Gap. A majority of the bush frog sister lineages were isolated on adjacent massifs, and signatures of range stasis provide support for the dominance of geological processes in allopatric speciation. In situ diversification events within the montane zones (more than 1800 m) of the two highest massifs suggest a role for climate-mediated forest-grassland persistence. Independent transitions along elevational gradients among sub-clades during the Miocene point to diversification along the elevational gradient. The study highlights the evolutionary significance of massifs in the Western Ghats with the high elevations acting as centres of lineage diversification and the low- and mid-elevations of the southern regions, with deeply divergent lineages, serving as museums.

以印度半岛西高止山脉（Western Ghats）为代表的热带生物多样性热点区域，其高物种多样性背后的历史演化过程至今仍鲜为人知。本研究在西高止山脉陡崖带的13个山地地块（massifs）开展灌树蛙（bush frogs）采样，探究了第四纪冰期、生态梯度与地质作用对支系（lineage）与演化支（clade）空间分布格局的相对影响。研究结果显示存在一次大规模的原地辐射演化（in situ radiation），涵盖超过60个支系，该演化过程呈现地理结构特征且具有演化支水平的特有性，同时存在南北两支深度分化的姐妹演化支，凸显了古河谷帕尔加特山口（Palghat Gap）的生物地理学意义。多数灌树蛙的姐妹支系均分布于相邻的山地地块中，而分布区停滞（range stasis）的分子信号支持地质作用在异地物种形成（allopatric speciation）过程中占据主导地位。两个海拔最高的山地地块的山地带（海拔超过1800米）内发生的原地分化事件，表明气候介导的森林-草原生境存续对支系分化具有推动作用。中新世（Miocene）期间，各亚演化支沿海拔梯度发生的独立演化转变，表明海拔梯度驱动了支系分化。本研究凸显了西高止山脉山地地块的演化意义：高海拔区域为支系分化中心，而南部区域的中低海拔地带（分布有深度分化的支系）则扮演了演化博物馆的角色。