Data from: Environment not dispersal limitation drives clonal composition of arctic Daphnia in a recently deglaciated area

One of the most prominent manifestations of the ongoing climate warming is the retreat of glaciers and ice sheets around the world. Retreating glaciers result in the formation of new ponds and lakes, which are available for colonization. The gradual appearance of these new habitat patches allows us to determine to what extent the composition of asexual Daphnia (water flea) populations is affected by environmental drivers versus dispersal limitation. Here we used a landscape genetics approach to assess the processes structuring the clonal composition of species in the D. pulex species complex that have colonized periglacial habitats created by ice-sheet retreat in western Greenland. We analyzed 61 populations from a young (<50 y) and an old cluster (>150 y) of lakes and ponds. We identified 42 asexual clones that varied widely in spatial distribution. Beta diversity was higher among older than among younger systems. Lineage sorting by the environment explained 14% of the variation in clonal composition whereas the pure effect of geographic distance was very small and statistically insignificant (Radj2 = 0.010, p= 0.085). Dispersal limitation did not seem important, even among young habitat patches. The observation of several tens of clones colonizing the area combined with environmentally-driven clonal composition of populations illustrates that population assembly of asexual species in the arctic is structured by environmental gradients reflecting differences in the ecology of clones.当前气候变暖最显著的表征之一，便是全球范围内冰川与冰盖的消融退缩。冰川消融退缩会催生新的池塘与湖泊，为生物定植提供了可利用的生境斑块。这些新生境斑块的逐步形成，使得我们能够解析：无性繁殖水蚤（Daphnia，俗称water flea）的种群组成，分别受环境驱动因子与扩散限制影响的程度。本研究采用景观遗传学（landscape genetics）方法，对格陵兰西部冰盖消融退缩形成的冰缘生境中，已定植的蚤状溞（D. pulex）物种复合群的克隆组成构建过程进行评估。本研究共分析了61个种群，这些种群分别来自两类湖泊与池塘集群：一类形成时长不足50年（<50 y），另一类则形成超过150年（>150 y）。研究共鉴定出42个无性繁殖克隆，其空间分布差异显著。β多样性（Beta diversity）在古老集群中的水平显著高于年轻集群。环境介导的谱系分选可解释14%的克隆组成变异，而地理距离的纯效应则极为微弱且无统计学显著性（Radj²=0.010，p=0.085）。即便在年轻生境斑块中，扩散限制对种群结构的影响也并不显著。本区域已有数十个克隆完成定植，且种群克隆组成受环境因子驱动，这一观测结果表明：北极地区无性繁殖物种的种群组装过程，由反映克隆生态位差异的环境梯度所塑造。