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.太平洋关岛的棕树蛇（Boiga irregularis）种群已跻身现代最具破坏性的外来入侵物种之列，成为极具标志性的入侵类群，但迄今尚无公开研究借助遗传数据明确其来源种群。本研究采用多遗传标记的DNA序列数据，结合基于溯祖（coalescent）的系统发育方法，将关岛种群置于棕树蛇原生分布全域的系统地理学大框架中进行定位，并检验该岛种群的遗传变异模式是否符合单一或多源种群引入的假说。我们还构建了多组人口统计学情景模型，各组模型在关岛入侵后即刻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）评估了各模拟结果与观测数据的拟合程度。本研究结果排除了来自不同来源种群的连续引入情形，证实关岛棕树蛇种群的唯一来源为巴布亚新几内亚北海岸外的阿德默勒尔蒂群岛（Admiralty Archipelago）。该发现与“二战末期军事搬迁过程中，棕树蛇被意外运至关岛”的假说一致。人口统计学模型对比结果表明，有多个体从来源地被转运至关岛，但仅不足10个个体参与了该种群的建立。本研究同时证实，奠基者效应（founder event）引发的遗传多样性匮乏并未阻碍棕树蛇在关岛的生态扩张与成功定殖，且为利用经典生物防治手段管控蛇类种群密度提供了独特的“遗传切入点”。