Data from: Testing for multiple invasion routes and source populations for the invasive brown treesnake (Boiga irregularis) on Guam: implications for pest management

The brown treesnake (Boiga irregularis) population on the Pacific island of Guam has reached iconic status as one of the most destructive invasive species of modern times, yet no published works have used genetic data to identify a source population. We used DNA sequence data from multiple genetic markers and coalescent-based phylogenetic methods to place the Guam population within the broader phylogeographic context of B. irregularis across its native range and tested whether patterns of genetic variation on the island are consistent with one or multiple introductions from different source populations. We also modeled a series of demographic scenarios that differed in the effective size and duration of a population bottleneck immediately following the invasion on Guam, and measured the fit of these simulations to the observed data using approximate Bayesian computation. Our results exclude the possibility of serial introductions from different source populations, and instead verify a single origin from the Admiralty Archipelago off the north coast of Papua New Guinea. This finding is consistent with the hypothesis that B. irregularis was accidentally transported to Guam during military relocation efforts at the end of World War II. Demographic model comparisons suggest that multiple snakes were transported to Guam from the source locality, but that fewer than 10 individuals could be responsible for establishing the population. Our results also provide evidence that low genetic diversity stemming from the founder event has not been a hindrance to the ecological success of B. irregularis on Guam, and at the same time offers a unique ‘genetic opening’ to manage snake density using classical biological approaches.

太平洋岛国关岛的棕树蛇（Boiga irregularis）种群，作为现代最具破坏性的入侵物种之一，已成为标志性类群，但目前尚无公开研究借助遗传数据确定其源种群。我们采用来自多个遗传标记的DNA序列数据，结合基于溯祖理论（coalescent theory）的系统发育分析方法，将关岛种群置于棕树蛇原生分布范围内的整体系统地理学框架中，并检验了岛上的遗传变异模式是否符合单次或多次来自不同源种群的引种事件。我们还构建了一系列种群人口统计学情景，这些情景在入侵关岛后立即出现的种群瓶颈的有效种群大小与持续时长上存在差异，并通过近似贝叶斯计算（approximate Bayesian computation）评估了这些模拟结果与观测数据的契合度。研究结果排除了来自不同源种群的连续引种的可能性，证实关岛棕树蛇种群的唯一起源地为巴布亚新几内亚北海岸外的阿德米勒尔蒂群岛。这一发现与“棕树蛇在第二次世界大战末期的军事搬迁行动中被意外携带至关岛”的假说相符。种群人口统计学模型对比结果显示，有多个体从源种群被携带至关岛，但仅不足10个个体即可建立该入侵种群。我们的研究还表明，奠基者效应（founder effect）导致的低遗传多样性并未阻碍棕树蛇在关岛的生态成功，同时也为通过经典生物防治方法调控蛇类种群密度提供了独特的“遗传切入点”。