Aars J, Dallas J F, Piertney S B, Marshall F, Gow J L, Telfer S, Lambin X
NERC Molecular Genetics in Ecological Initiative, School of Biological Science, Aberdeen, Scotland, UK.
Mol Ecol. 2006 May;15(6):1455-66. doi: 10.1111/j.1365-294X.2006.02889.x.
Theory predicts that the impact of gene flow on the genetic structure of populations in patchy habitats depends on its scale and the demographic attributes of demes (e.g. local colony sizes and timing of reproduction), but empirical evidence is scarce. We inferred the impact of gene flow on genetic structure among populations of water voles Arvicola terrestris that differed in average colony sizes, population turnover and degree of patchiness. Colonies typically consisted of few reproducing adults and several juveniles. Twelve polymorphic microsatellite DNA loci were examined. Levels of individual genetic variability in all areas were high (H(O) = 0.69-0.78). Assignments of juveniles to parents revealed frequent dispersal over long distances. The populations showed negative F(IS) values among juveniles, F(IS) values around zero among adults, high F(ST) values among colonies for juveniles, and moderate, often insignificant, F(ST) values for parents. We inferred that excess heterozygosity within colonies reflected the few individuals dispersing from a large area to form discrete breeding colonies. Thus pre-breeding dispersal followed by rapid reproduction results in a seasonal increase in differentiation due to local family groups. Genetic variation was as high in low-density populations in patchy habitats as in populations in continuous habitats used for comparison. In contrast to most theoretical predictions, we found that populations living in patchy habitats can maintain high levels of genetic variability when only a few adults contribute to breeding in each colony, when the variance of reproductive success among colonies is likely to be low, and when dispersal between colonies exceeds nearest-neighbour distances.
理论预测，基因流对斑块状栖息地中种群遗传结构的影响取决于其规模以及群落的人口统计学属性（例如当地群体大小和繁殖时间），但实证证据却很少。我们推断了基因流对普通田鼠（Arvicola terrestris）种群间遗传结构的影响，这些种群在平均群体大小、种群更替和斑块程度上存在差异。群体通常由少数繁殖成年个体和几只幼体组成。研究了12个多态性微卫星DNA位点。所有区域的个体遗传变异水平都很高（H(O)=0.69 - 0.78）。将幼体与亲本进行配对分析发现存在频繁的长距离扩散。这些种群中，幼体的F(IS)值为负，成年个体的F(IS)值接近零，幼体在群体间的F(ST)值很高，而亲本的F(ST)值中等，且往往不显著。我们推断，群体内杂合子过剩反映了少数个体从大片区域扩散而来，形成离散的繁殖群体。因此，繁殖前扩散随后快速繁殖导致因当地家庭群体而产生的季节性分化增加。与连续栖息地中的种群相比，斑块状栖息地中低密度种群的遗传变异同样很高。与大多数理论预测相反，我们发现，当每个群体中只有少数成年个体参与繁殖，当群体间繁殖成功率的方差可能较低，以及当群体间的扩散距离超过最近邻距离时，生活在斑块状栖息地中的种群仍能维持高水平的遗传变异。
