Data from: Defining spatial and temporal patterns of phylogeographic structure in Madagascar's iguanid lizards (Genus Oplurus)

Understanding the remarkably high species diversity and levels of endemism found among Madagascar’s flora and fauna has been the focus of many studies. One hypothesis that has received much attention proposes that Pleistocene climate fluctuations spurred diversification. However, while spatial patterns of distribution and phylogenetic relationships can provide support for biogeographic predictions, temporal estimates of divergence are required to determine the fit of these geospatial patterns to climatic or biogeographic mechanisms. We use multilocus DNA sequence data to test whether divergence times among Malagasy iguanid lizards of the subfamily Oplurinae are compatible with a hypotheses of Quaternary diversification. We estimate the oplurine species tree and associated divergence times under a relaxed clock model. In addition, we examine the phylogeographic structure and population divergence times within two sister-species of Oplurus primarily distributed in the northwest and southwest of Madagascar (O. cuvieri and O. cyclurus, respectively). We find that divergence events among oplurine lineages occurred in the Oligocene and Miocene and are thus far older and incompatible with the hypothesis that recent climate fluctuations are related to current species diversity. However, the timing of intraspecific divergences and spatial patterns of population genetic structure within O. cuvieri and O. cyclurus suggest a role for both intrinsic barriers and recent climate fluctuations at population-level divergences. Integrating information across spatial and temporal scales allows us to identify and better understand the mechanisms generating patterns diversity.

解析马达加斯加动植物区系中极高的物种多样性与特有性水平，长期以来都是诸多研究的核心研究议题。其中一项广受关注的假说提出，更新世（Pleistocene）气候波动驱动了类群分化。尽管物种分布的空间格局与系统发育关系能够为生物地理学预测提供佐证，但要验证这些地理空间格局是否契合气候或生物地理机制，仍需获取分化时间的时序估算结果。本研究利用多位点DNA序列数据，检验马达加斯加鬣蜥科（Iguanidae）平尾鬣蜥亚科（Oplurinae）蜥蜴的类群分化时间是否符合第四纪（Quaternary）分化假说。我们基于宽松分子钟模型（relaxed clock model），对平尾鬣蜥亚科的物种树及其对应的分化时间进行了估算。此外，我们还针对两种姊妹物种展开研究：分别为主要分布于马达加斯加西北部的库氏平尾鬣蜥（Oplurus cuvieri）与西南部的环尾平尾鬣蜥（Oplurus cyclurus），解析其系统地理学结构与种群分化时间。研究结果表明，平尾鬣蜥亚科类群的分化事件发生于渐新世（Oligocene）与中新世（Miocene），其年代远早于第四纪，因此与“近期气候波动与当前物种多样性存在关联”的假说相悖。不过，库氏平尾鬣蜥与环尾平尾鬣蜥的种内分化时间以及种群遗传结构的空间格局显示，内在屏障与近期气候波动均对种群水平的分化发挥了作用。整合不同空间与时间尺度的相关信息，能够帮助我们识别并更深入地理解塑造物种多样性格局的核心机制。