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 (...针对入侵物种种群适应性演化变化的研究，可通过联合应用数量遗传学（quantitative genetics）与种群遗传学（population genetics）方法得以推进。本研究以千屈菜（purple loosestrife）为模式系统，通过对比欧洲本土种群与北美入侵种群的表型分化及中性遗传分化开展QST-FST分析，以此探究自然选择（natural selection）、遗传漂变（genetic drift）与基因流（gene flow）在物种入侵过程中的相对作用。研究结果显示，入侵种群与本土种群的扩增片段长度多态性（AFLP, Amplified Fragment Length Polymorphism）变异水平相当，该模式与从多样欧洲基因库进行多次独立引种的结果相符。不过研究观察到，后续入侵过程中遗传变异出现降低，这或许由奠基者效应（founder effects）与遗传漂变所致。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）进行对比后发现，并无证据表明存在歧化选择（QST > FST）或稳定选择（...