Data from: Frequent and parallel habitat transitions as driver of unbounded radiations in the Cape flora

The enormous species richness in the Cape Floristic Region (CFR) of Southern Africa is the result of numerous radiations, but the temporal progression and possible mechanisms of these radiations are still poorly understood. Here, we explore the macroevolutionary dynamics of the Restionaceae, that include 340 species which are found in all vegetation types in the Cape flora and are ecologically dominant in fynbos. Using an almost complete (i.e. 98%) species-level time calibrated phylogeny and models of diversification dynamics, we show that species diversification is constant through the Cenozoic, with no evidence of an acceleration with the onset of the modern winter-wet climate, or a recent density-dependent slowdown. Contrary to expectation, species inhabiting the oldest (montane) and most extensive (drylands) habitats did not undergo higher diversification rates than species in the younger (lowlands) and more restricted (wetland) habitats. We show that the rate of habitat transitions is more closely related to the speciation rate than to time, and that more than a quarter of all speciation events are associated with habitat transitions. This suggests that the unbounded Restionaceae diversification resulted from numerous, parallel, habitat shifts, rather than persistence in an habitat stimulating speciation. We speculate that this could be one of the mechanisms resulting in the hyper-diverse Cape flora.

南非开普植物区（Cape Floristic Region, CFR）拥有极高的物种丰富度，这源于多次辐射演化事件，但这类辐射演化的时间进程与潜在机制仍不甚明晰。本研究聚焦帚灯草科（Restionaceae）的宏观演化动力学：该科包含340个物种，遍布开普植物区的所有植被类型，且在芬博斯灌丛（fynbos）中占据生态主导地位。借助覆盖98%物种的近乎完整的物种水平时间校准系统发育树，结合多样化动力学模型，我们的研究结果显示：新生代（Cenozoic）以来，物种多样化速率始终保持恒定，既未出现随现代冬季湿润气候形成而加速的迹象，也未观测到近期的密度依赖型速率放缓现象。与学界预期相悖的是，栖息于最古老生境（山地）与分布最广生境（旱地）的物种，其多样化速率并未高于栖息于较年轻生境（低地）与分布更受限生境（湿地）的物种。我们还发现，生境转换速率与物种形成速率（speciation rate）的相关性远高于其与时间的相关性，且超过四分之一的物种形成事件均伴随生境转换过程。这表明，帚灯草科的无限制辐射演化，源于多次平行的生境转移事件，而非物种长期存续于某一固定生境以推动物种形成。我们推测，这一机制或为造就开普植物区超高物种丰富度的潜在原因之一。