Data from: Comparative genetic structure and demographic history in endemic Galápagos weevils

The challenge of maintaining genetic diversity within populations can be exacerbated for island endemics if they display population dynamics and behavioral attributes that expose them to genetic drift without the benefits of gene-flow. We assess patterns of genetic structure and demographic history in twenty seven populations of nine species of flightless endemic Galápagos weevils from nine of the islands and one winged introduced close relative. Analysis of mitochondrial DNA reveals significant population structure and moderately variable, though demographically stable, populations for lowland endemics (Fst= 0.094 to 0.541; π: 0.014 to 0.042; Mismatch p=0.003 to 0.026 and D (Tajima)=-0.601to1.203), in contrast to signals of past contractions and expansions in highland specialists on two islands (Mismatch p=0.003 to 0.026 and D (Tajima)=-0.601to1.203). We interpret this series of variable and highly structured population groups as a system of long-established independently founded island units, where structuring could be a signal of micro-allopatric differentiation due to patchy host plant distribution and poor dispersal abilities. We suggest that the severe reduction and subsequent increase of suitably moist habitat that accompanied past climatic variation could have contributed to the observed population fluctuations in highland specialists. We propose the future exploration of hybridization between the introduced and highland endemic species on Santa Cruz, especially given the expansion of the introduced species into the highlands, the sensitivity to past climatic variation detected in highland populations and the potentially threatened state of single-island endemics.维持种群内遗传多样性的挑战，对于岛屿特有种而言可能进一步加剧——若其种群动态与行为特征使其暴露于遗传漂变的影响之下，却未能获得基因流（gene flow）的增益。本研究针对采自9座加拉帕戈斯群岛的9个无翅特有象鼻虫物种、共计27个种群，以及1个具翅的近缘引入种，展开分析以解析其遗传结构模式与种群历史动态。线粒体DNA（mitochondrial DNA）分析结果显示，低地特有种种群呈现显著的遗传结构与中等水平的遗传变异，且种群规模整体保持稳定（遗传分化系数Fst值区间为0.094至0.541；核苷酸多样性π值区间为0.014至0.042；错配分布检验p值区间为0.003至0.026，塔伊马D统计量（Tajima's D）区间为-0.601至1.203）；与之形成鲜明对比的是，两座岛屿上的高地特化种则呈现出过往种群收缩与扩张的遗传信号（错配分布检验p值区间为0.003至0.026，塔伊马D统计量区间为-0.601至1.203）。我们将这一系列具有变异且高度结构化的种群类群，解读为长期独立形成的岛屿种群单元体系：其遗传结构可能是因宿主植物分布呈斑块状、物种扩散能力薄弱而引发的微异域分化信号。我们推测，伴随过去气候波动而发生的适宜湿润生境的剧烈缩减与后续扩张，可能是高地特化种种群波动的重要诱因。我们建议未来可针对圣克鲁斯岛上的引入种与高地特有种开展杂交相关研究，尤其需考虑到以下因素：引入种正向高地区域扩张、高地种群对过往气候波动具有较高敏感性，以及单岛特有种可能面临的濒危状态。