Data from: Dispersal ability and habitat requirements determine landscape-level genetic patterns in desert aquatic insects

Species occupying the same geographic range can exhibit remarkably different population structures across the landscape, ranging from highly diversified to panmictic. Given limitations on collecting population-level data for large numbers of species, ecologists seek to identify proximate organismal traits—such as dispersal ability, habitat preference and life history—that are strong predictors of realized population structure. We examined how dispersal ability and habitat structure affect the regional balance of gene flow and genetic drift within three aquatic insects that represent the range of dispersal abilities and habitat requirements observed in desert stream insect communities. For each species, we tested for linear relationships between genetic distances and geographic distances using Euclidean and landscape-based metrics of resistance. We found that the moderate-disperser Mesocapnia arizonensis (Plecoptera: Capniidae) has a strong isolation-by-distance pattern, suggesting migration–drift equilibrium. By contrast, population structure in the flightless Abedus herberti (Hemiptera: Belostomatidae) is influenced by genetic drift, while gene flow is the dominant force in the strong-flying Boreonectes aequinoctialis (Coleoptera: Dytiscidae). The best-fitting landscape model for M. arizonensis was based on Euclidean distance. Analyses also identified a strong spatial scale-dependence, where landscape genetic methods only performed well for species that were intermediate in dispersal ability. Our results highlight the fact that when either gene flow or genetic drift dominates in shaping population structure, no detectable relationship between genetic and geographic distances is expected at certain spatial scales. This study provides insight into how gene flow and drift interact at the regional scale for these insects as well as the organisms that share similar habitats and dispersal abilities.分布于同一地理区域的物种，其种群结构在景观尺度上可呈现显著差异，从高度分化的种群到泛交种群（panmictic）。鉴于对大量物种开展种群水平数据采集存在诸多局限，生态学家旨在识别可有效预测实际种群结构的核心生物性状，例如扩散能力、生境偏好与生活史特征。本研究选取了三类可代表荒漠溪流昆虫群落中扩散能力与生境需求梯度的水生昆虫类群，探究扩散能力与生境结构如何调控区域尺度下基因流（gene flow）与遗传漂变（genetic drift）之间的动态平衡。针对每个物种，我们分别采用欧氏距离（Euclidean distance）与基于景观的抗性度量指标，检验遗传距离与地理距离间的线性关联。研究发现，中等扩散能力的Mesocapnia arizonensis（襀翅目（Plecoptera）：襀科（Capniidae））呈现出显著的距离隔离（isolation-by-distance）模式，表明其处于迁移-漂变平衡状态。与之形成鲜明对比的是，无翅的Abedus herberti（半翅目（Hemiptera）：负子蝽科（Belostomatidae））的种群结构主要受遗传漂变调控，而强飞行能力的Boreonectes aequinoctialis（鞘翅目（Coleoptera）：龙虱科（Dytiscidae））的种群结构则以基因流为主导。针对M. arizonensis的最优景观模型基于欧氏距离构建。分析结果同时揭示了显著的空间尺度依赖性：景观遗传学（landscape genetics）方法仅在扩散能力处于中等水平的物种中表现良好。本研究结果表明，当基因流或遗传漂变其中一方主导种群结构的塑造过程时，在特定空间尺度下将无法检测到遗传距离与地理距离间的关联。本研究不仅阐明了上述昆虫类群在区域尺度下基因流与遗传漂变的互作模式，同时也为具有相似生境与扩散能力的其他生物类群的相关研究提供了重要参考。