Data from: Genetic status and timing of a weevil introduction to Santa Cruz Island, Galápagos

Successful invasive species can overcome or circumvent the potential genetic loss caused by an introduction bottleneck through a rapid population expansion and admixture from multiple introductions. We explore the genetic makeup and the timing of a species introduction to Santa Cruz Island in the Galápagos archipelago. We investigate the presence of processes that can maintain genetic diversity in populations of the broad-nosed weevil Galapaganus howdenae howdenae. Analyses of combined genotypes for 8 microsatellite loci showed evidence of past population size reductions through moment and likelihood-based estimators. No evidence of admixture through multiple introductions was found, but substantial current population sizes (N0 298, 95% HPD 50-2300), genetic diversity comparable to long-established endemics (Mean number of alleles=3.875) and lack of genetic structure across the introduced range (ΦST = 0.01359) could suggest that foundations are in place for populations to rapidly recover any loss of genetic variability. The time estimates for the introduction into Santa Cruz support an accidental transfer during the colonization period (1832-1959) pre-dating the spurt in human population growth. Our evaluation of the genetic status of G. h. howdenae suggests potential for population growth in addition to our field observations of a concurrent expansion in range and feeding preferences towards protected areas and endemic host plants.成功的入侵物种可通过快速种群扩张以及多源引种的遗传混合效应，克服或规避引种瓶颈所引发的潜在遗传多样性丢失。本研究针对加拉帕戈斯群岛圣克鲁兹岛的物种引种事件，探究其种群遗传构成与引种时间，并以宽喙象甲（broad-nosed weevil）Galapaganus howdenae howdenae为研究对象，调查其种群中能够维持遗传多样性的潜在过程。对8个微卫星位点（microsatellite loci）的联合基因型进行分析后，通过矩估计法与似然估计法，检测到该种群曾经历过种群规模缩减的信号。未发现多源引种引发遗传混合的证据，但当前种群规模可观（有效种群大小N₀=298，95%最高后验密度（Highest Posterior Density, HPD）区间为50~2300），其遗传多样性可与长期定殖的特有物种相媲美（平均等位基因数=3.875），且在引种分布范围内未检测到遗传结构分化（ΦST=0.01359），这些结果表明该种群具备快速恢复遗传变异丢失的基础条件。针对圣克鲁兹岛引种时间的估算结果显示，该物种的意外引入发生在群岛殖民时期（1832-1959年），早于当地人口增长的爆发阶段。结合野外观测到的该象甲种群分布范围持续扩张、取食偏好转向保护区及特有寄主植物的现象，本研究对G. h. howdenae遗传现状的评估结果显示其具备种群增长的潜力。