Winkler Gesche, Dodson Julian J, Lee Carol Eunmi
Québec-Océan, Département de Biologie, Université Laval, Pavillon Vachon, Québec, Canada G1K 7P4.
Mol Ecol. 2008 Jan;17(1):415-30. doi: 10.1111/j.1365-294X.2007.03480.x. Epub 2007 Sep 14.
Invasive species are often composed of highly differentiated populations or sibling species distributed across their native ranges. This study analysed patterns of distribution and the evolutionary and demographic histories of populations within the native range of the copepod species complex Eurytemora affinis. Genetic structure was analysed for samples from 17 locations from both the invaded and native ranges in the St Lawrence River drainage basin, using 652 base pairs of the mitochondrial cytochrome oxidase subunit I gene. This study revealed a high degree of heterogeneity in genetic structure and habitat type in the native range, as well as a bias in the sources of invasive populations. Two genetically distinct clades showed a pattern of niche partitioning within the St Lawrence basin. The noninvasive North Atlantic clade primarily occupied the central portion of the St Lawrence Middle Estuary, whereas the invasive Atlantic clade was more prevalent along the margins, in the upstream reaches of the estuary and downstream salt marshes. Habitat partitioning and genetic subdivision was also present within the Atlantic clade. The freshwater populations were genetically more proximate to the Atlantic clade populations in the estuary than to those in the salt marsh, suggesting the estuary as the source of the invasive populations. The freshwater invading populations showed evidence of a modest population bottleneck. Populations from both clades showed genetic signatures of demographic population expansions that preceded the timing of the last glacial maximum, supporting the St Lawrence as a secondary contact zone between the two clades. Additional analyses on physiological and evolutionary properties of populations in the native range, along with analysis of the selection regime within native habitats, might yield insights into the evolutionary potential to invade.
入侵物种通常由分布在其原生范围内的高度分化的种群或近缘物种组成。本研究分析了桡足类物种复合体近亲真宽水蚤（Eurytemora affinis）原生范围内种群的分布模式、进化和种群历史。利用线粒体细胞色素氧化酶亚基I基因的652个碱基对，对圣劳伦斯河流域入侵范围和原生范围内17个地点的样本进行了遗传结构分析。本研究揭示了原生范围内遗传结构和栖息地类型的高度异质性，以及入侵种群来源的偏差。两个遗传上不同的分支在圣劳伦斯盆地内呈现出生态位划分模式。非入侵性的北大西洋分支主要占据圣劳伦斯河中游河口的中部，而入侵性的大西洋分支在边缘、河口上游和下游盐沼更为普遍。大西洋分支内也存在栖息地划分和遗传细分。淡水种群在基因上与河口的大西洋分支种群比与盐沼中的种群更接近，这表明河口是入侵种群的来源。淡水入侵种群显示出适度种群瓶颈的证据。两个分支的种群都显示出末次盛冰期之前种群扩张的遗传特征，支持圣劳伦斯河作为两个分支之间的次生接触带。对原生范围内种群的生理和进化特性进行进一步分析，以及对原生栖息地内的选择机制进行分析，可能会深入了解入侵的进化潜力。
