Data from: Critically endangered island endemic or peripheral population of a widespread species? Conservation genetics of Kikuchi’s gecko and the global challenge of protecting peripheral oceanic island endemic vertebrates

Aim: To highlight the significant conservation challenge of evaluating peripheral endemic vertebrates in island archipelago systems and to assess empirically the complexities of approaches to conservation genetic studies across political and biogeographic boundaries. To demonstrate the poignant need for international collaboration and coordination when species delimitation problems with high conservation concern involve island endemics with biogeographically peripheral ranges. Location: Southeast Asia, Lanyu Island, Taiwan, and the Philippines. Methods: Genetic samples were collected and sequenced for one mitochondrial gene and five nuclear loci for species of the Gekko mindorensis-G. kikuchii species complex in Southeast Asia. We used maximum likelihood and Bayesian phylogenetic methods and coalescent-based species delimitation analyses to estimate phylogeographic relationships, construct multilocus haplotype networks and test putative species boundaries. Results: Phylogenetic and population genetic analyses suggest that Kikuchi's Gecko may represent a peripheral population of a widespread species distributed from the northern Philippines to Taiwan. However, we identify a discrepancy between inferences of species boundaries resulting from methods based on allele frequencies versus coalescent-based methods that incorporate evolutionary history. Coalescent-based analyses suggest that G. kikuchii may be a distinct evolutionary lineage. Our study underscores the need for coalescent-based methods in conjunction with population genetic approaches for conservation genetic assessments of widespread species. Main conclusions: This study joins a few recent works suggesting that Philippine-derived anomalies in the fauna of Lanyu (and possibly greater Taiwan) are worthy of careful reconsideration. Determining whether each is the result of recent human-mediated introduction or (possibly more ancient) natural dispersal should be the goal of future studies on this seldom-conceived biogeographic relationship. Isolated species endemic to islands on the outer periphery of biogeographic and political regions represent particular conservation challenges. This is especially true if a species occurs on an isolated island that is allied biogeographically with one nation, but politically administered by another.

研究目的：阐明岛屿群岛系统中边缘特有脊椎动物评估所面临的重大保护难题，并以实证手段评估跨政治与生物地理边界开展保护遗传学研究的方法复杂性；同时证明，当涉及具有高保护优先级的物种界定问题、且该问题关联生物地理边缘分布的岛屿特有物种时，国际协作与协调的迫切必要性。
研究区域：东南亚、中国台湾兰屿岛以及菲律宾。
研究方法：针对东南亚地区曼岛壁虎-菊池壁虎（Gekko mindorensis-G. kikuchii）物种复合体类群，采集其遗传样本并对1个线粒体基因（mitochondrial gene）与5个核基因座（nuclear loci）进行测序。本研究采用最大似然法（maximum likelihood）、贝叶斯系统发育方法（Bayesian phylogenetic methods）以及基于溯祖理论的物种界定分析（coalescent-based species delimitation analyses），以推断系统地理学关系、构建多基因座单倍型网络（multilocus haplotype networks），并检验推定的物种边界。
研究结果：系统发育与种群遗传学分析表明，菊池壁虎（Kikuchi's Gecko）可能是分布于菲律宾北部至台湾地区的广布物种的边缘种群。然而，本研究发现，基于等位基因频率的物种边界推断结果，与纳入进化历史信息的基于溯祖理论的方法所得结果存在不一致。基于溯祖理论的分析显示，菊池壁虎（G. kikuchii）可能是一个独立的进化支系。本研究强调，在对广布物种开展保护遗传学评估时，需将基于溯祖理论的方法与种群遗传学手段相结合。
主要结论：本研究与近期少数研究成果一致，表明兰屿岛（乃至更广泛的台湾地区）动物区系中源自菲律宾的异常类群值得审慎重新评估。针对这类鲜少被探讨的生物地理关系，未来研究的核心目标应在于明确这些类群究竟是近期人类介导引入的结果，还是（可能更为古老的）自然扩散的产物。分布于生物地理与政治区域外围岛屿的孤立特有物种，面临着特殊的保护挑战；若某一物种栖息在生物地理上隶属于某一国家、但政治上由另一国家管辖的偏远岛屿时，这一挑战尤为突出。