Data from: Large-scale phylogeny of chameleons suggests African origins and rapid Eocene radiation

Oceanic dispersal has emerged as an important factor contributing to biogeographic patterns in numerous taxa. Chameleons are a clear example of this, as they are primarily found in Africa and Madagascar, but the age of the family is post-Gondwanan break-up. A Malagasy origin for the family has been suggested, yet this hypothesis has not been tested using modern biogeographic methods with a dated phylogeny. To examine competing hypotheses of African and Malagasy origins, we generated a dated phylogeny using between six and 13 genetic markers, for up to 174 taxa representing greater than 90 per cent of all named species. Using three different ancestral-state reconstruction methods (Bayesian and likelihood approaches), we show that the family most probably originated in Africa, with two separate oceanic dispersals to Madagascar during the Palaeocene and the Oligocene, when prevailing oceanic currents would have favoured eastward dispersal. Diversification of genus-level clades took place in the Eocene, and species-level diversification occurred primarily in the Oligocene. Plio-Pleistocene speciation is rare, resulting in a phylogeny dominated by palaeo-endemic species. We suggest that contraction and fragmentation of the Pan-African forest coupled to an increase in open habitats (savannah, grassland, heathland), since the Oligocene played a key role in diversification of this group through vicariance.

海洋扩散（Oceanic dispersal）业已成为塑造众多类群生物地理格局的关键因素之一。变色龙（Chameleons）即为典型例证：该类群主要分布于非洲与马达加斯加，但其所属科的起源时间晚于冈瓦纳大陆解体时期。此前有假说提出该科起源于马达加斯加，但该假说尚未结合时间校准系统发育树（dated phylogeny）采用现代生物地理学方法开展检验。为验证非洲起源与马达加斯加起源这两种相互竞争的假说，本研究针对多达174个涵盖该科90%以上已命名物种的类群，利用6至13个遗传标记构建了时间校准系统发育树。通过贝叶斯法、极大似然法等三种不同的祖先状态重建（ancestral-state reconstruction）方法，研究结果表明：避役科最可能起源于非洲，并分别在古新世与渐新世发生了两次独立的海洋扩散至马达加斯加的事件——彼时盛行的洋流更利于向东扩散。该类群的属级分支分化发生于始新世，而物种级分化主要发生于渐新世；上新世-更新世的物种形成事件极为罕见，最终形成了以古特有种（palaeo-endemic species）为主的系统发育结构。我们推测：自渐新世以来，泛非森林的收缩与碎片化，以及开阔生境（稀树草原、草原、灌丛）的扩张，通过地理分异（vicariance）过程深刻推动了该类群的分化。