PDF(Pubmed)
Abstract：
When populations repeatedly adapt to similar environments they can evolve similar phenotypes based on shared genetic mechanisms (parallel evolution). The likelihood of parallel evolution is affected by demographic history, as it depends on the standing genetic variation of the source population. The three-spined stickleback (Gasterosteus aculeatus) repeatedly colonized and adapted to brackish and freshwater. Most parallel evolution studies in G. aculeatus were conducted at high latitudes, where freshwater populations maintain connectivity to the source marine populations. Here, we analysed southern and northern European marine and freshwater populations to test two hypotheses. First, that southern European freshwater populations (which currently lack connection to marine populations) lost genetic diversity due to bottlenecks and inbreeding compared to their northern counterparts. Second, that the degree of genetic parallelism is higher among northern than southern European freshwater populations, as the latter have been subjected to strong drift due to isolation. The results show that southern populations exhibit lower genetic diversity but a higher degree of genetic parallelism than northern populations. Hence, they confirm the hypothesis that southern populations have lost genetic diversity, but this loss probably happened after they had already adapted to freshwater conditions, explaining the high degree of genetic parallelism in the south.
摘要：
当种群反复适应相似的环境时，他们可以基于共同的遗传机制（平行进化）进化出相似的表型。平行进化的可能性受到人口历史的影响，因为它取决于源种群的常备遗传变异。三刺刺背鱼（Gasterosteusaculeatus）反复定殖并适应微咸和淡水。大多数的平行进化研究都是在高纬度地区进行的，淡水种群与海洋种群保持连通性。这里,我们分析了南欧和北欧的海洋和淡水种群，以检验两个假设。首先,南欧淡水种群（目前与海洋种群缺乏联系）由于瓶颈和近亲繁殖而失去了遗传多样性。第二,北欧淡水种群的遗传平行程度高于南欧淡水种群，因为后者由于隔离而受到强烈的漂移。结果表明，南方种群的遗传多样性较低，但遗传平行程度高于北方种群。因此，他们证实了南方人口已经失去遗传多样性的假设，但是这种损失可能发生在他们已经适应淡水条件之后，解释了南方的高度遗传平行性。
