Viviparous reproduction has evolved independently more than 100 times in the evolutionary history of Squamata (lizards and snakes). Adaptation to cold climates is the dominant hypothesis explaining shifts to viviparity, but viviparous species are also present in the tropical lowlands, implying the presence of other factors that may also promote the evolution of viviparity. For example, the tropical Asian/Oceanian subfamily, Draconinae, includes two viviparous genera (Cophotis and Harpesaurus). However, one of them, Harpesaurus, is extremely rare, making it difficult to study aspects of their ecology or evolution. We managed to collect a H. borneensis, and this provided an opportunity to address the evolution of viviparity in draconine lizards. Based on a new molecular phylogenetic hypothesis, including all viviparous groups in Draconinae, we infer that viviparity has evolved twice within the subfamily. Ancestral state reconstruction analyses indicated that shifts to viviparity were preceded by the evolution of arboreality and slow-moving locomotion. Our analysis strongly suggests evolutionary correlations between habitats, locomotion, and reproductive modes. Taken together, these results suggest that the use of arboreal habitats and slow locomotion facilitated the evolution of viviparity in these tropical/subtropical lizards. Arboreal, slow-moving species are considered to rely more on crypsis in predator avoidance rather than fleeing. Therefore, we propose that such species are relatively insusceptible to the concomitant cost of viviparity: reduced locomotive ability and increased risk of predation during pregnancy. We also describe and discuss the unique behaviours of H. borneensis.

中文翻译：

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奇异蜥蜴 Harpesaurus 的系统发育位置暗示了 Draconinae（有鳞目：Agamidae）的树栖、运动和繁殖模式之间的共同进化

在有鳞目（蜥蜴和蛇）的进化史上，胎生繁殖独立进化了100多次。对寒冷气候的适应是解释向胎生转变的主要假设，但热带低地也存在胎生物种，这意味着存在其他可能促进胎生进化的因素。例如，热带亚洲/大洋洲亚科 Draconinae 包括两个胎生属（Cophotis 和 Harpesaurus）。然而，其中之一，Harpesaurus，极为罕见，因此很难研究其生态或进化的各个方面。我们设法收集了一只 H. borneensis，这为研究龙蜥蜥的胎生进化提供了机会。基于一种新的分子系统发育假说，包括天龙亚科中的所有胎生类群，我们推断胎生在亚科内进化了两次。祖先状态重建分析表明，向胎生转变之前是树栖和缓慢移动的进化。我们的分析强烈表明栖息地、运动和繁殖模式之间的进化相关性。总之，这些结果表明，使用树栖栖息地和缓慢的运动促进了这些热带/亚热带蜥蜴的胎生进化。树栖的、行动缓慢的物种被认为更多地依赖于躲避捕食者而不是逃跑的隐秘。因此，我们建议这些物种相对不易受胎生的伴随成本的影响：降低的运动能力和怀孕期间被捕食的风险增加。我们还描述和讨论了 H.