Data from: Genetic variation and structure of house sparrow populations: is there an island effect?

Population genetic structure and intrapopulation levels of genetic variation have important implications for population dynamics and evolutionary processes. Habitat fragmentation is one of the major threats to biodiversity. It leads to smaller population sizes and reduced gene flow between populations and will thus also affect genetic structure. We use a natural system of island and mainland populations of house sparrows along the coast of Norway to characterize the different population genetic properties of fragmented populations. We genotyped 636 individuals distributed across 14 populations at 15 microsatellite loci. The level of genetic differentiation was estimated using F-statistics and specially designed Mantel tests were conducted to study the influence of population type (i.e. mainland or island) and geographic distance on the genetic population structure. Furthermore, the effects of population type, population size and latitude on the level of genetic variation within populations were examined. Our results suggest that genetic processes on islands and mainland differed in two important ways. First, the intrapopulation level of genetic variation tended to be lower and the occurrence of population bottlenecks more frequent on islands than the mainland. Second, although the general level of genetic differentiation was low to moderate, it was higher between island populations than between mainland populations. However, differentiation increased in mainland populations somewhat faster with geographical distance. These results suggest that population bottleneck events and genetic drift have been more important in shaping the genetic composition of island populations compared with populations on the mainland. Such knowledge is relevant for a better understanding of evolutionary processes and conservation of threatened populations.

种群遗传结构与种群内遗传变异水平，对种群动态及进化过程具有重要意义。栖息地破碎化是威胁生物多样性的主要因素之一，其会导致种群规模缩小、种群间基因流减弱，进而对遗传结构产生影响。本研究以挪威海岸沿线的家麻雀海岛与大陆种群为自然研究系统，旨在解析破碎化种群的各类种群遗传特征。我们对分布于14个种群的636个个体，在15个微卫星位点（microsatellite loci）上进行了基因分型；采用F统计量（F-statistics）估算遗传分化水平，并通过特制的曼特尔检验（Mantel test）分析种群类型（即大陆或海岛）与地理距离对种群遗传结构的影响。此外，本研究还探究了种群类型、种群规模与纬度对种群内遗传变异水平的影响。研究结果显示，海岛与大陆种群的遗传过程存在两点显著差异：其一，相较于大陆种群，海岛种群的种群内遗传变异水平普遍更低，且种群瓶颈（population bottleneck）事件的发生频率更高；其二，尽管整体遗传分化水平处于低至中等程度，但海岛种群间的遗传分化程度高于大陆种群，不过大陆种群的遗传分化随地理距离增加的增速略快于海岛种群。上述结果表明，相较于大陆种群，种群瓶颈事件与遗传漂变（genetic drift）在塑造海岛种群的遗传组成过程中发挥了更为关键的作用。该研究结果有助于更深入地理解进化过程，并为受威胁种群的保护工作提供理论支撑。