Data from: Multilocus phylogeny and Bayesian estimates of species boundaries reveal hidden evolutionary relationships and cryptic diversity in Southeast Asian monitor lizards

Recent conceptual, technological, and methodological advances in phylogenetics have enabled increasingly robust statistical species delimitation in studies of biodiversity. As the variety of evidence purporting species diversity has increased, so too have the kinds of tools and inferential power of methods for delimiting species. Here we showcase an organismal system for a data-rich, comparative molecular approach to evaluating strategies of species delimitation among monitor lizards of the genus Varanus. The water monitors (Varanus salvator Complex), a widespread group distributed throughout Southeast Asia and southern India, have been the subject of numerous taxonomic treatments, which have drawn recent attention due to the possibility of undocumented species diversity. To date, studies of this group have relied on purportedly diagnostic morphological characters, with no attention given to the genetic underpinnings of species diversity. Using a 5-gene dataset, we estimated phylogeny and used multilocus genetic networks, analysis of population structure, and a Bayesian coalescent approach to infer species boundaries. Our results contradict previous systematic hypotheses, reveal surprising relationships between island and mainland lineages, and uncover novel, cryptic evolutionary lineages (i.e. new putative species). Our study contributes to a growing body of literature suggesting that, used in concert with other sources of data (e.g., morphology, ecology, biogeography), multilocus genetic data can be highly informative to systematists and biodiversity specialists when attempting to estimate species diversity and identify conservation priorities. We recommend holding in abeyance taxonomic decisions until multiple, converging lines of evidence are available to best inform taxonomists, evolutionary biologists, and conservationists.

近年来，系统发育学（phylogenetics）在概念、技术与方法层面的进展，使得生物多样性研究中的物种界定（species delimitation）统计分析愈发稳健可靠。随着支撑物种多样性的证据类型日益丰富，用于物种界定的工具种类与方法推论能力也同步提升。本研究针对巨蜥属（Varanus）巨蜥类群，展示了一套用于评估物种界定策略的数据密集型比较分子研究范式。泽巨蜥复合群（Varanus salvator Complex）是广泛分布于东南亚与印度南部的类群，此前已有多项分类学研究对其开展系统探讨，而近期因其存在未被记录的物种多样性潜力而受到广泛关注。迄今为止，该类群的相关研究均依赖所谓的鉴别形态特征，尚未关注物种多样性的遗传基础。本研究利用五基因数据集（5-gene dataset）构建系统发育树，并通过多基因遗传网络、种群结构分析以及贝叶斯溯祖方法（Bayesian coalescent approach）推断物种边界（species boundaries）。研究结果与此前的分类学假说相悖，揭示了岛屿支系与大陆支系间出人意料的亲缘关系，并发现了全新的隐蔽进化支系（即新的推定物种（putative species））。本研究为日益增多的相关文献提供了实证支撑：当分类学家与生物多样性研究者试图估算物种多样性、确定保护优先级时，若将多基因遗传数据与形态学、生态学、生物地理学等其他数据源结合使用，可提供极具价值的科学信息。我们建议暂不作出分类学决策，直至获取多源佐证证据，从而为分类学家、进化生物学家与保护工作者提供最充分的决策依据。