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.

持续的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。退缩的冰川会形成新的池塘与湖泊，为生物定植提供了可利用的生境。这些新生境斑块的逐步形成，使得我们得以量化评估：无性繁殖的水蚤（Daphnia，water flea）种群组成在多大程度上受环境驱动因子与扩散限制的调控。本研究采用景观遗传学方法，针对定植于格陵兰西部冰盖退缩所形成的冰缘生境的蚤状溞（D. pulex）物种复合群，解析调控其克隆组成的生态过程。我们共分析了两类湖泊与池塘集群的61个种群：一类为形成时长不足50年的年轻集群，另一类为形成超过150年的古老集群。研究共鉴定出42个无性繁殖克隆，其空间分布差异显著。古老生境集群的β多样性显著高于年轻生境集群。环境介导的谱系分选可解释克隆组成14%的变异；而地理距离的纯效应则极小，且统计学上不显著（校正决定系数R²_adj=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。本研究中数十个克隆成功定植该区域，且种群克隆组成受环境调控的观测结果表明：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。