Data from: Rapid range expansion increases genetic differentiation while causing limited reduction in genetic diversity in a damselfly

Many ectothermic species are currently expanding their geographic range due to global warming. This can modify the population genetic diversity and structure of these species because of genetic drift during the colonization of new areas. Although the genetic signatures of historical range expansions have been investigated in an array of species, the genetic consequences of natural, contemporary range expansions have received little attention, with the only studies available focusing on range expansions along a narrow front. We investigate the genetic consequences of a natural range expansion in the Mediterranean damselfly Coenagrion scitulum, which is currently rapidly expanding along a broad front in different directions. We assessed genetic diversity and genetic structure using twelve microsatellite markers in five centrally located populations and five recently established populations at the edge of the geographic distribution. Our results suggest that, although a marginal significant decrease in the allelic richness was found in the edge populations, genetic diversity has been preserved during the range expansion of this species. Nevertheless, edge populations were genetically more differentiated compared to core populations, suggesting genetic drift during the range expansion. The smaller effective population sizes of the edge populations compared to central populations also suggest a contribution of genetic drift after colonization. We argue and document that range expansion along multiple axes of a broad expansion front generates little reduction in genetic diversity, yet stronger differentiation of the edge populations.

受全球变暖影响，目前许多外温物种正持续扩张其地理分布范围。此类扩张会因新区域定殖过程中的遗传漂变，改变该类物种种群的遗传多样性与群体遗传结构。尽管诸多物种的历史分布范围扩张所留下的遗传印记已被广泛研究，但针对当代自然分布范围扩张的遗传效应却鲜有关注，现有相关研究仅聚焦于沿狭窄前沿开展的扩张事件。本研究以当前正沿宽阔前沿向多个方向快速扩张分布范围的地中海蟌（*Coenagrion scitulum*）为研究对象，探究其天然分布范围扩张的遗传效应。本研究采用12个微卫星（microsatellite）标记，对5个位于分布区中部的种群以及5个新近在地理分布边缘建立的种群进行了遗传多样性与群体遗传结构分析。研究结果显示：尽管边缘种群的等位基因丰富度出现了边际显著下降，但该物种在分布范围扩张过程中，其遗传多样性得以保留。尽管如此，边缘种群相较于中部种群表现出更高的遗传分化程度，这表明该物种在分布范围扩张过程中发生了遗传漂变。边缘种群的有效种群规模小于中部种群，这同样表明定殖后发生了遗传漂变的作用。本研究论证并证实：沿宽阔扩张前沿多轴方向开展的分布范围扩张，虽不会对遗传多样性造成显著降低，却会加剧边缘种群的遗传分化程度。