Data from: Comparison of quantitative and molecular genetic variation of native vs. invasive populations of purple loosestrife (Lythrum salicaria L., Lythraceae)

Study of adaptive evolutionary changes in populations of invasive species can be advanced through the joint application of quantitative and population genetic methods. Using purple loosestrife as a model system, we investigated the relative roles of natural selection, genetic drift, and gene flow in the invasive process by contrasting phenotypic and neutral genetic differentiation among native European and invasive North American populations (QST - FST analysis). Our results indicate that invasive and native populations harbor comparable levels of AFLP variation, a pattern consistent with multiple independent introductions from a diverse European gene pool. However, it was observed that the genetic variation reduced during subsequent invasion, perhaps by founder effects and genetic drift. Comparison of genetically-based quantitative trait differentiation (QST) to its expectation under neutrality (FST) revealed no evidence of disruptive selection (QST > FST) or stabilizing selection (QST < FST). One exception was found for only one trait (the number of stems) showing significant sign of stabilizing selection across all populations. It suggests that the difficulties in distinguishing the effects of non-adaptive population processes and natural selection. Multiple introductions of purple loosestrife may have created a genetic mixture from diverse source populations and increased population genetic diversity, but its link to the adaptive differentiation of invasive North American populations needs further research.

入侵物种种群适应性演化变化的相关研究，可通过联合应用数量遗传学与群体遗传学方法得以推进。本研究以千屈菜（purple loosestrife）为模式系统，通过对比欧洲原生种群与北美入侵种群的表型分化与中性遗传分化并开展QST-FST分析，探究了自然选择、遗传漂变与基因流在物种入侵过程中的相对作用。研究结果显示，入侵种群与原生种群的扩增片段长度多态性（AFLP）变异水平相当，该模式与来自多样欧洲基因库的多次独立引种事件相符。不过研究观察到，后续入侵过程中种群遗传变异出现降低现象，推测可能由奠基者效应与遗传漂变导致。将基于遗传的数量性状分化（QST）与中性预期下的分化水平（FST）进行对比，未发现分裂选择（QST > FST）或稳定选择（QST < FST）的相关证据。仅在茎秆数量这一个性状上，观察到覆盖所有研究种群的显著稳定选择信号。该结果提示，难以区分非适应性种群过程与自然选择的作用效应。千屈菜的多次引种事件可能形成了来自不同源种群的遗传混合，提升了种群遗传多样性，但其与北美入侵种群适应性分化之间的关联仍需进一步研究。