Data from: Pleistocene range dynamics in the eastern Greater Cape Floristic Region: a case study of the Little Karoo endemic Berkheya cuneata (Asteraceae)

The glacial–interglacial climate cycles of the Pleistocene played a significant role in dramatically altering species distributions across the globe. However, the climate of the Greater Cape Floristic Region is thought to have been decoupled from global fluctuations and the current Mediterranean climate remained relatively buffered during this period. Here we explore the roles of climate stability and the topographic complexity of the region on the range history of an endemic Little Karoo plant, Berkheya cuneata, using ensemble species distribution modelling and multi-locus phylogeography. The species distribution models projected onto downscaled climate simulation of the Last Glacial Maximum demonstrated a considerable range contraction and fragmentation into the western and eastern Little Karoo, separated by the Rooiberg inselberg. This population fragmentation is mirrored in the phylogeographic structuring of both chloroplast and nuclear DNA. These results suggest that sufficient climatic buffering coupled with regionally complex topography ensured the localised population persistence during Pleistocene climate cycles but these features have also promoted population vicariance in this, and likely other, Little Karoo lowland species.

更新世（Pleistocene）的冰期-间冰期气候旋回（glacial–interglacial climate cycles）曾显著重塑全球物种分布格局。然而学界普遍认为，大开普植物区（Greater Cape Floristic Region）的气候与全球气候波动脱耦，在此期间当地的地中海气候（Mediterranean climate）始终保持相对稳定的缓冲状态。本研究针对小卡鲁盆地（Little Karoo）特有植物楔叶伯克希亚（Berkheya cuneata），采用集成物种分布模型（ensemble species distribution modelling）与多位点谱系地理学（multi-locus phylogeography）方法，探究该区域气候稳定性与地形复杂性对其分布历史的调控作用。
基于末次冰盛期（Last Glacial Maximum）降尺度气候模拟（downscaled climate simulation）结果构建的物种分布模型显示，该物种的分布范围曾发生显著收缩，并被罗伊贝格岛状山（Rooiberg inselberg）分隔为东西两个小卡鲁种群，呈现出明显的片段化特征。这一种群片段化现象，与叶绿体DNA（chloroplast DNA）及核DNA（nuclear DNA）所展现的谱系地理学结构高度一致。
本研究结果表明，充足的气候缓冲效应与区域复杂地形共同保障了该物种在更新世气候旋回中的局域种群存续，同时这些特征也推动了本研究对象及其他可能的小卡鲁低地物种发生种群隔离分化（population vicariance）。