Comparative Landscape Genetics of Three Closely Related Sympatric Hesperid Butterflies with Diverging Ecological Traits

To understand how landscape characteristics affect gene flow in species with diverging ecological traits, it is important to analyze taxonomically related sympatric species in the same landscape using identical methods. Here, we present such a comparative landscape genetic study involving three closely related Hesperid butterflies of the genus Thymelicus that represent a gradient of diverging ecological traits. We analyzed landscape effects on their gene flow by deriving inter-population connectivity estimates based on different species distribution models (SDMs), which were calculated from multiple landscape parameters. We then used SDM output maps to calculate circuit-theoretic connectivity estimates and statistically compared these estimates to actual genetic differentiation in each species. We based our inferences on two different analytical methods and two metrics of genetic differentiation. Results indicate that land use patterns influence population connectivity in the least mobile specialist T. acteon. In contrast, populations of the highly mobile generalist T. lineola were panmictic, lacking any landscape related effect on genetic differentiation. In the species with ecological traits in between those of the congeners, T. sylvestris, climate has a strong impact on inter-population connectivity. However, the relative importance of different landscape factors for connectivity varies when using different metrics of genetic differentiation in this species. Our results show that closely related species representing a gradient of ecological traits also show genetic structures and landscape genetic relationships that gradually change from a geographical macro- to micro-scale. Thus, the type and magnitude of landscape effects on gene flow can differ strongly even among closely related species inhabiting the same landscape, and depend on their relative degree of specialization. In addition, the use of different genetic differentiation metrics makes it possible to detect recent changes in the relative importance of landscape factors affecting gene flow, which likely change as a result of contemporary habitat alterations.为探明景观特征如何影响具有分化生态特征的物种的基因流，采用统一方法对同域分布的近缘分类群开展分析具备重要意义。本研究针对3种隶属于Thymelicus属的近缘弄蝶科蝴蝶（Hesperid butterflies）开展此类比较景观遗传学研究，这些物种恰好构成了生态特征逐步分化的梯度序列。我们通过基于多种景观参数计算得到的不同物种分布模型（species distribution models, SDMs）推导种群间连通性估算值，以此分析景观对其基因流的影响；随后利用物种分布模型的输出图层，计算电路理论连通性估算值，并将这些估算值与各物种的实际遗传分化进行统计学比较。本研究的推断基于两种不同的分析方法与两类遗传分化指标。研究结果显示，土地利用模式对移动能力最弱的特化种T. acteon的种群连通性存在显著影响。与之相反，移动能力极强的泛化种T. lineola的种群呈泛交状态，未表现出任何与景观相关的遗传分化效应。对于生态特征介于上述两个同属物种之间的T. sylvestris，气候因子对其种群间连通性具有强烈影响。然而，当针对该物种使用不同的遗传分化指标时，不同景观因子对连通性的相对重要性会发生变化。我们的研究结果表明，代表生态特征梯度的近缘物种，其遗传结构与景观遗传关系也会呈现出从地理宏观尺度到微观尺度的逐步变化。由此可见，即便栖息于同一景观的近缘物种，景观对基因流的作用类型与强度也可能存在显著差异，且这一差异取决于它们各自的特化程度。此外，采用不同的遗传分化指标，能够检测到影响基因流的景观因子相对重要性的近期变化，而此类变化大概率由当代生境改变所引发。