S12-Modeltests.R from Their fates intertwined: diversification patterns of the Asian gliding vertebrates may have been forged by dipterocarp trees

The repeated evolution of gliding in diverse Asian vertebrate lineages is hypothesized to have been triggered by the dominance of tall dipterocarp trees in the tropical forests of Southeast Asia. These dipterocarp forests have acted as both centres of diversification and climatic refugia for gliding vertebrates, and support most of their extant diversity. We predict similarities in the diversification patterns of dipterocarp trees and gliding vertebrates, and specifically test whether episodic diversification events such as rate shifts and/or mass extinctions were temporally congruent in these groups. We analysed diversification patterns in reconstructed timetrees of Asian dipterocarps, the most speciose gliding vertebrates from different classes (Draco lizards, gliding frogs and Pteromyini squirrels) and compared them with similar-sized clades of non-gliding relatives (Diploderma lizards, Philautus frogs and Callosciurinae squirrels) from Southeast Asia. We found significant declines in net-diversification rates of dipterocarps and the gliding vertebrates during the Pliocene–Pleistocene, but not in the non-gliding groups. We conclude that the homogeneity and temporal coincidence of these rate declines point to a viable ecological correlation between dipterocarps and the gliding vertebrates. Further, we suggest that while the diversification decay in dipterocarps was precipitated by post-Miocene aridification of Asia, the crises in the gliding vertebrates were induced by both events concomitantly.

学界假说认为，亚洲不同脊椎动物支系中反复出现的滑翔演化事件，是由东南亚热带森林中高大的龙脑香科树木（dipterocarp trees）占据主导地位所驱动的。这些龙脑香林既是滑翔脊椎动物（gliding vertebrates）的物种分化中心与气候避难所，也承载了该类群绝大多数现存的物种多样性。本研究预测龙脑香科树木与滑翔脊椎动物的物种分化模式存在相似性，并专门检验了这两类群中诸如分化速率转变或大规模灭绝等间歇性分化事件是否在时间上一致。我们对亚洲龙脑香科植物、不同类群中物种最丰富的滑翔脊椎动物——包括飞蜥属蜥蜴（Draco lizards）、滑翔蛙类（gliding frogs）以及鼯鼠族松鼠（Pteromyini squirrels）——的重建时间树（timetrees）中的分化模式进行了分析，并将其与东南亚地区非滑翔近亲类群的等规模演化支进行了对比，这些非滑翔近亲类群包括龙蜥属蜥蜴（Diploderma lizards）、小树蛙属蛙类（Philautus frogs）以及丽松鼠亚科松鼠（Callosciurinae squirrels）。我们发现，在上新世-更新世（Pliocene–Pleistocene）期间，龙脑香科树木与滑翔脊椎动物的净分化速率均出现了显著下降，而非滑翔类群则未出现这一现象。本研究据此认为，这类分化速率下降的同质性与时间重合性，表明龙脑香科树木与滑翔脊椎动物之间存在可靠的生态关联。此外，本研究提出，尽管龙脑香科植物的分化衰退是由亚洲中新世后的干旱化（aridification）所引发，但滑翔脊椎动物所面临的生存危机则是由这两类事件共同诱发的。