Differing, multi-scale landscape effects on genetic diversity and differentiation in eastern chipmunks

Understanding how habitat loss and fragmentation impact genetic variation is a major goal in landscape genetics, but to date, most studies have focused solely on the correlation between intervening matrix and genetic differentiation at a single spatial scale. Several caveats exist in these study designs, among them is the inability to include measures of genetic diversity in addition to differentiation. Both genetic metrics help predict population persistence, but are expected to function at differing spatial scales, which requires a multi-scale investigation. In this study, we sampled two distinct spatial scales in 31 independent landscapes along a gradient of landscape context (i.e., forest amount, configuration, and types of intervening matrix) to investigate how landscape heterogeneity influences genetic diversity and differentiation in the forest-associated eastern chipmunk (Tamias striatus). Overall, quality of intervening matrix was correlated with genetic differentiation at multiple spatial scales, whereas only configuration was associated with regional scale genetic diversity. Habitat amount, in contrast, did not influence genetic differentiation or diversity at either spatial scale. Based on our findings, landscape effects on genetic variation appears to differ based on spatial scale, the type of genetic response variable, and random variation among landscapes, making extrapolation of results from single scale, un-replicated studies difficult. We encourage landscape geneticists to utilize multi-scale, replicated landscapes with both genetic diversity and differentiation to gain a more comprehensive understanding of how habitat loss and fragmentation influence genetic variation.探究生境丧失与片段化如何影响遗传变异是景观遗传学（landscape genetics）的核心研究目标之一，但迄今为止，多数研究仅聚焦于单一空间尺度下景观基质（intervening matrix）与遗传分化（genetic differentiation）之间的相关性。此类研究设计存在诸多局限，其中之一便是除遗传分化外，无法纳入遗传多样性（genetic diversity）的相关测度。两类遗传指标均有助于预测种群存续能力，但其作用尺度存在差异，因此需要开展多尺度研究。 本研究沿景观背景（即森林面积、配置格局及景观基质类型）梯度，在31个独立景观中设置两个不同的空间尺度，以此探究景观异质性（landscape heterogeneity）对与森林生境相关的东部花栗鼠（Tamias striatus）的遗传多样性与遗传分化的影响。整体而言，景观基质质量与多空间尺度下的遗传分化呈显著相关，而仅景观配置格局与区域尺度的遗传多样性存在关联。与之相对，生境面积并未对任一空间尺度下的遗传分化与遗传多样性产生影响。 基于本研究结果，景观对遗传变异的影响因空间尺度、遗传响应变量类型以及景观间的随机变异而异，这使得基于单一尺度、未设置重复的研究结果进行外推变得困难。我们呼吁景观遗传学者采用包含遗传多样性与遗传分化两类指标的多尺度、重复设置景观的研究设计，以更全面地揭示生境丧失与片段化对遗传变异的影响机制。