Mardulyn Patrick, Milinkovitch Michel C
Laboratory of Evolutionary Genetics, Université Libre de Bruxelles, Rue Jeener et Brachet 12, 6041 Gosselies, Belgium.
Mol Ecol. 2005 May;14(6):1641-53. doi: 10.1111/j.1365-294X.2005.02537.x.
We have studied mitochondrial DNA variation in a local population of the leaf beetle species Gonioctena olivacea, to check whether its apparent low dispersal behaviour affects its pattern of genetic variation at a small geographical scale. We have sampled 10 populations of G. olivacea within a rectangle of 5 x 2 km in the Belgian Ardennes, as well as five populations located approximately along a straight line of 30 km and separated by distances of 3-12 km. For each sampled individual (8-19 per population), a fragment of the mtDNA control region was polymerase chain reaction-amplified and sequenced. Sequence data were analysed to test whether significant genetic differentiation could be detected among populations separated by such relatively short distances. The reconstructed genealogy of the mitochondrial haplotypes was also used to investigate the demographic history of these populations. Computer simulations of the evolution of populations were conducted to assess the minimum amount of gene flow that is necessary to explain the observed pattern of variation in the samples. Results show that migration among populations included in the rectangle of 5 x 2 km is substantial, and probably involves the occurrence of dispersal flights. This appears difficult to reconcile with the results of a previous ecological field study that concluded that most of this species dispersal occurs by walking. While sufficient migration to homogenize genetic diversity occurs among populations separated by distances of a few hundred metres to a few kilometres, distances greater than 5 km results in contrast in strong differentiation among populations, suggesting that migration is drastically reduced on such distances. Finally, the results of coalescent simulations suggest that the star-like genealogy inferred from the mtDNA sequence data is fully compatible with a past demographic expansion. However, a metapopulation structure alone (without the need to invoke a population expansion event) cannot be dismissed as the cause of this star shape.
我们研究了叶甲物种橄榄色角胸叶甲当地种群的线粒体DNA变异，以检验其明显的低扩散行为是否会在小地理尺度上影响其遗传变异模式。我们在比利时阿登地区一个5×2公里的矩形区域内采集了10个橄榄色角胸叶甲种群的样本，以及大约沿着一条30公里长的直线分布、相距3 - 12公里的5个种群的样本。对于每个采样个体（每个种群8 - 19个），对线粒体DNA控制区的一个片段进行聚合酶链反应扩增并测序。分析序列数据以检验在如此相对短距离分隔的种群之间是否能检测到显著的遗传分化。线粒体单倍型的重建谱系也用于研究这些种群的种群历史。进行了种群进化的计算机模拟，以评估解释样本中观察到的变异模式所需的最小基因流数量。结果表明，在5×2公里矩形区域内的种群之间迁移很显著，可能涉及扩散飞行的发生。这似乎难以与之前一项生态实地研究的结果相协调，该研究得出结论，该物种的大多数扩散是通过步行进行的。虽然在相隔几百米到几公里的种群之间发生了足以使遗传多样性同质化的迁移，但大于5公里的距离会导致种群之间强烈的分化，这表明在这样的距离上迁移急剧减少。最后，合并模拟的结果表明，从线粒体DNA序列数据推断出的星状谱系与过去的种群扩张完全兼容。然而，不能排除仅由集合种群结构（无需引入种群扩张事件）作为这种星状形状的原因。
