Data from: The influence of landscape on gene flow in the eastern massasauga rattlesnake (Sistrurus c. catenatus): insight from computer simulations

Understanding how gene flow shapes contemporary population structure requires the explicit consideration of landscape composition and configuration. New landscape genetic approaches allow us to link such heterogeneity to gene flow within and among populations. However, the attribution of cause is difficult when landscape features are spatially correlated, or when genetic patterns reflect past events. We use spatial Bayesian clustering and landscape resistance analysis to identify the landscape features that influence gene flow across two regional populations of the eastern massasauga rattlesnake, Sistrurus c. catenatus. Based on spatially explicit simulations, we inferred how habitat distribution modulates gene flow and attempted to disentangle the effects of spatially confounded landscape features. We found genetic clustering across one regional landscape but not the other, and also local differences in the effect of landscape on gene flow. Beyond the effects of isolation-by-distance, water bodies appear to underlie genetic differentiation among individuals in one regional population. Significant effects of roads were additionally detected locally, but these effects are possibly confounded with the signal of water bodies. In contrast, we found no signal of isolation-by-distance or landscape effects on genetic structure in the other regional population. Our simulations imply that these local differences have arisen as a result of differences in population density or tendencies for juvenile rather than adult dispersal. Importantly, our simulations also demonstrate that the ability to detect the consequences of contemporary anthropogenic landscape features (e.g. roads) on gene flow may be compromised when long-standing natural features (e.g. water bodies) co-exist on the landscape.

解析基因流如何塑造当代种群结构，需明确考量景观组成与景观配置。新兴景观遗传学方法可将此类景观异质性与种群内部及种群间的基因流建立关联。但当景观特征存在空间相关性，或遗传格局反映历史事件时，因果归因颇具挑战。本研究采用空间贝叶斯聚类（spatial Bayesian clustering）与景观阻力分析（landscape resistance analysis），针对东部马萨苏加响尾蛇（Sistrurus c. catenatus）的两个区域种群，识别出影响其基因流的关键景观特征。基于空间显式模拟，本研究推断生境分布对基因流的调控作用，并尝试厘清空间混淆景观特征所带来的效应。研究发现，其中一个区域景观存在遗传聚类现象，另一区域则未出现；同时，景观对基因流的影响在两地存在局部差异。除距离隔离（isolation-by-distance）效应外，水体似乎是导致其中一个区域种群内个体间遗传分化的核心因素。此外，局部区域还检测到道路的显著效应，但该效应可能与水体的信号存在混淆。与之形成鲜明对比的是，另一区域种群未检测到距离隔离信号，亦未发现景观对遗传结构的影响。本研究的模拟结果表明，此类局部差异源于种群密度差异，或是幼体而非成体的扩散倾向差异。尤为重要的是，模拟结果还证实，当长期存在的自然景观特征（如水体）与当代人为景观特征（如道路）共存时，检测后者对基因流影响的能力可能会受到削弱。