Data from: Functional connectivity in replicated urban landscapes in the land snail (Cornu aspersum)

Urban areas are highly fragmented and thereby exert strong constraints on individual dispersal. Despite this, some species manage to persist in urban areas, such as the garden snail, Cornu aspersum, which is common in cityscapes despite its low mobility. Using landscape genetic approaches, we combined study area replication and multi-scale analysis to determine how landscape composition, configuration, and connectivity influence snail dispersal across urban areas. At the overall landscape scale, areas with a high percentage of roads decreased genetic differentiation between populations. At the population scale, genetic differentiation was positively linked with building surface, the proportion of borders where wooded patches and roads appeared side-by-side and the proportion of borders combining wooded patches and other impervious areas. Analyses based on pairwise genetic distances validated the isolation-by-distance and isolation-by-resistance models for this land snail, with an equal fit to least-cost paths and circuit-theory-based models. Each of the 12 landscapes analyzed separately yielded specific relations to environmental features, whereas analyses integrating all replicates highlighted general common effects. Our results suggest that urban transport infrastructures facilitate passive snail dispersal. At a local scale, corresponding to active dispersal, unfavorable habitats (wooded and impervious areas) isolate populations. This work upholds the use of replicated landscapes to increase the generalizability of landscape genetics results, and shows how multi-scale analyses provide insight to scale-dependent processes.城市区域具有高度的生境破碎化特征，由此对个体扩散形成强烈限制。尽管如此，仍有部分物种得以在城市区域存续，例如庭园蜗牛（Cornu aspersum），尽管其移动能力较弱，却在城市景观中颇为常见。本研究借助景观遗传学（landscape genetics）方法，结合多研究区域重复采样与多尺度分析，探究景观组成、构型与连通性如何影响蜗牛在城市区域内的扩散过程。在整体景观尺度上，道路占比较高的区域会降低种群间的遗传分化。在种群尺度上，遗传分化与建筑用地占比、森林斑块与道路毗邻的边界比例，以及森林斑块与其他不透水地表组合的边界比例呈正相关关系。基于成对遗传距离的分析验证了该陆生蜗牛的距离隔离（isolation-by-distance）与阻力隔离（isolation-by-resistance）模型，其对最小成本路径（least-cost paths）模型与基于电路理论的模型（circuit-theory-based models）拟合效果相当。分别对12个景观进行独立分析时，其结果均与环境特征呈现出特异性关联；而整合所有重复采样区域的分析则揭示了普适性的共同效应。本研究结果表明，城市交通基础设施可促进蜗牛的被动扩散；而在对应主动扩散的局域尺度上，不适生境（森林斑块与不透水地表）会加剧种群间的隔离。本研究证实了采用重复景观采样可提升景观遗传学研究结果的可推广性，并阐明了多尺度分析如何为尺度依赖过程提供解析视角。