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.

占据相同地理分布区的物种，其景观尺度下的种群结构可呈现显著差异，涵盖高度分化至泛交（panmictic）的多种类型。鉴于对大量物种收集种群水平数据存在局限，生态学家致力于识别可有效预测实际种群结构的关键生物性状，例如扩散能力、生境偏好与生活史。本研究以3种代表沙漠溪流昆虫群落中已观测到的扩散能力与生境需求梯度的水生昆虫为对象，探讨扩散能力与生境结构如何影响区域尺度下基因流与遗传漂变的相对平衡。针对每个物种，我们分别采用欧氏距离（Euclidean）与基于景观的抗性指标，检验遗传距离与地理距离间的线性关联。
研究发现，中等扩散能力的亚利桑那短石蝇（Mesocapnia arizonensis，襀翅目：短石蝇科Plecoptera: Capniidae）呈现显著的距离隔离（isolation-by-distance）模式，暗示其处于迁移-漂变平衡状态。与之相反，无翅的赫氏负子蝽（Abedus herberti，半翅目：负子蝽科Hemiptera: Belostomatidae）的种群结构受遗传漂变主导，而强飞行能力的宽翅龙虱（Boreonectes aequinoctialis，鞘翅目：龙虱科Coleoptera: Dytiscidae）的种群结构则以基因流为主要驱动力。亚利桑那短石蝇的最优拟合景观模型基于欧氏距离。分析结果还揭示了显著的空间尺度依赖性：景观遗传学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单独主导种群结构形成时，在特定空间尺度下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3种昆虫在区域尺度下基因流与遗传漂变的相互作用模式，也为具有相似生境与扩散能力的其他生物提供了相关研究视角。