Data from: Diversity change during the rise of tetrapods and the impact of the ‘Carboniferous Rainforest Collapse’

The Carboniferous and early Permian were critical intervals in the diversification of early four-limbed vertebrates (tetrapods), yet the major patterns of diversity and biogeography during this time remain unresolved. Previous estimates suggest that global tetrapod diversity rose continuously across this interval and that habitat fragmentation following the ‘Carboniferous Rainforest Collapse’ (CRC) drove increased endemism among communities. However, previous work failed to adequately account for spatial and temporal biases in sampling. Here, we reassess early tetrapod diversity and biogeography with a new global species-level dataset using sampling standardisation and network biogeography methods. Our results support a tight relationship between observed richness and sampling, particularly during the Carboniferous. We found that subsampled species richness initially increased into the late Carboniferous, then decreased substantially across the Carboniferous/Permian boundary before slowly recovering in the early Permian. Our analysis of biogeography does not support the hypothesis that the CRC drove endemism; instead, we found evidence for increased cosmopolitanism in the early Permian. While a changing environment may have played a role in reducing diversity in the earliest Permian, our results suggest that the CRC was followed by increased global connectivity between communities, possibly reflecting both reduced barriers to dispersal and the diversification of amniotes.

石炭纪（Carboniferous）与早二叠世是早期四足脊椎动物（tetrapods）辐射演化的关键时段，但该时期的主要多样性格局与生物地理模式仍未明晰。既往研究推测，全球四足动物多样性在此期间持续增长，且“石炭纪雨林崩溃（Carboniferous Rainforest Collapse, CRC）”引发的生境破碎化，推动了群落间特有性的提升。然而，以往研究未能充分考量采样过程中的时空偏差问题。本研究依托一套全新的全球物种级数据集，结合采样标准化方法与网络生物地理学手段，重新评估了早期四足动物的多样性与生物地理格局。研究结果证实，观测物种丰富度与采样强度之间存在显著关联，尤以石炭纪时期最为突出。我们发现，经校正后的物种丰富度在晚石炭世初期持续升高，随后在石炭纪-二叠纪界线处出现大幅下降，直至早二叠世才逐步缓慢恢复。针对生物地理格局的分析并不支持“石炭纪雨林崩溃推动特有性提升”的假说；与之相反，我们在早二叠世发现了类群广布性增强的证据。尽管环境变化可能在早二叠世早期的多样性降低过程中起到了一定作用，但本研究结果表明，石炭纪雨林崩溃之后，不同群落间的全球连通性反而有所提升，这一现象可能同时源于扩散障碍的减弱与羊膜动物（amniotes）的辐射演化。