Herborg Leif-Matthias, Weetman David, van Oosterhout Cock, Hänfling Bernd
School of Marine Science & Technology, University of Newcastle upon Tyne, Newcastle upon Tyne, UK.
Mol Ecol. 2007 Jan;16(2):231-42. doi: 10.1111/j.1365-294X.2006.03133.x.
Genetic studies of recently established populations are challenging because the assumption of equilibrium underlying many analyses is likely to be violated. Using microsatellites, we investigated determinants of genetic structure and migration among invasive European-Chinese mitten crab populations, applying a combination of traditional population genetic analyses and nonequilibrium Bayesian methods. Consistent with their recent history, invasive populations showed much lower levels of genetic diversity than a native Chinese population, indicative of recent bottlenecks. Population differentiation was generally low but significant and especially pronounced among recently established populations. Significant differentiation among cohorts from the same geographical location (River Thames) suggests the low effective population size and associated strong genetic drift that would be anticipated from a very recent colonization. An isolation-by-distance pattern appears to be driven by an underlying correlation between geographical distance and population age, suggesting that cumulative homogenizing gene flow reduces founder bottleneck-associated genetic differentiation between longer-established populations. This hypothesis was supported by a coalescent analysis, which supported a drift + gene flow model as more likely than a model excluding gene flow. Furthermore, admixture analysis identified several recent migrants between the UK and Continental European population clusters. Admixture proportions were significantly predicted by the volume of shipping between sites, indicating that human-mediated transport remains a significant factor for dispersal of mitten crabs after the initial establishment of populations. Our study highlights the value of nonequilibrium methods for the study of invasive species, and also the importance of evaluating nonequilibrium explanations for isolation by distance patterns.
对新建立的种群进行遗传学研究具有挑战性，因为许多分析所依据的平衡假设可能会被打破。我们使用微卫星，结合传统的种群遗传学分析和非平衡贝叶斯方法，研究了入侵欧洲的中华绒螯蟹种群之间遗传结构和迁移的决定因素。与它们的近期历史一致，入侵种群的遗传多样性水平远低于中国的一个本地种群，这表明近期存在瓶颈效应。种群分化总体较低，但很显著，在新建立的种群中尤为明显。来自同一地理位置（泰晤士河）的不同群体之间存在显著分化，这表明有效种群规模较小以及由此产生的强烈遗传漂变，这是近期殖民化过程中预期会出现的情况。距离隔离模式似乎是由地理距离和种群年龄之间的潜在相关性驱动的，这表明累积的同质化基因流减少了长期建立的种群之间与奠基者瓶颈相关的遗传分化。这一假设得到了溯祖分析的支持，该分析支持漂移 + 基因流模型比不包括基因流的模型更有可能。此外，混合分析确定了英国和欧洲大陆种群集群之间的几个近期迁移者。混合比例可通过地点之间的航运量显著预测，这表明在种群初步建立后，人类介导的运输仍然是中华绒螯蟹扩散的一个重要因素。我们的研究强调了非平衡方法在入侵物种研究中的价值，以及评估距离隔离模式的非平衡解释的重要性。
