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入的遗传混合效应，克服或规避引种瓶颈所引发的潜在遗传多样性丢失风险。本研究聚焦加拉帕戈斯群岛圣克鲁斯岛的物种引种事件，探究其种群遗传构成与引种时间节点，并以宽喙象鼻虫（Galapaganus howdenae howdenae）为研究对象，调查其种群中维持遗传多样性的相关过程是否存在。对8个微卫星位点（microsatellite loci）的联合基因型分析结果显示，基于矩估计与似然估计法的分析均证实该种群曾经历过种群规模缩减事件。未发现存在多源引种引发的遗传混合现象，但当前种群规模可观（有效种群大小N₀=298，95%最高后验密度（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），且在整个引种分布范围内未检测到显著遗传结构（遗传分化系数ΦST=0.01359），这些结果表明该种群具备快速修复遗传变异丢失的基础条件。针对圣克鲁斯岛引种时间的估算结果显示，该物种的引种为偶然传入，发生在加拉帕戈斯殖民时期（1832年~1959年），早于当地人口增长的爆发阶段。结合野外实地观测结果——该种群的分布范围与取食偏好均在同步扩张，且开始向保护区及特有寄主植物拓展——本研究对G. h. howdenae遗传现状的评估显示，其种群具备进一步增长的潜力。