An understanding of genetic structure is essential for answering many questions in population genetics. However, complex population dynamics and scale-dependent processes can make it difficult to detect if there are distinct genetic clusters present in natural populations. Inferring discrete population structure is particularly challenging in the presence of continuous genetic variation such as isolation by distance. Here, we use the plant species Mimulus guttatus as a case study for understanding genetic structure at three spatial scales. We use reduced-representation sequencing and marker-based genotyping to understand dispersal dynamics and to characterise genetic structure. Our results provide insight into the spatial scale of genetic structure in a widespread plant species, and demonstrate how dispersal affects spatial genetic variation at the local, regional, and range-wide scale. At a fine-spatial scale, we show dispersal is rampant with little evidence of spatial genetic structure within populations. At a regional-scale, we show continuous differentiation driven by isolation by distance over hundreds of kilometres, with broad geographic genetic clusters that span major barriers to dispersal. Across Western North America, we observe geographic genetic structure and the genetic signature of multiple postglacial recolonisation events, with historical gene flow linking isolated populations. Our genetic analyses show M. guttatus is highly dispersive and maintains large metapopulations with high intrapopulation variation. This high diversity and dispersal confounds the inference of genetic structure, with multi-level sampling and spatially-explicit analyses required to understand population history.

中文翻译：

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广布植物Mimulus guttatus中遗传结构和距离隔离的多层次模式

了解遗传结构对于回答群体遗传学中的许多问题至关重要。然而，复杂的种群动态和依赖于规模的过程可能使检测自然种群中是否存在不同的遗传簇变得困难。在存在连续遗传变异（例如按距离隔离）的情况下，推断离散种群结构尤其具有挑战性。在这里，我们使用植物物种 Mimulus guttatus 作为案例研究，以了解三个空间尺度的遗传结构。我们使用减少表征测序和基于标记的基因分型来了解分散动态并表征遗传结构。我们的结果提供了对广泛植物物种遗传结构空间尺度的洞察，并展示散布如何影响局部、区域和范围范围内的空间遗传变异。在精细的空间尺度上，我们表明扩散猖獗，几乎没有证据表明种群内的空间遗传结构。在区域尺度上，我们展示了由数百公里的距离隔离驱动的连续分化，具有跨越主要扩散障碍的广泛地理遗传簇。在整个北美西部，我们观察到地理遗传结构和多次冰后重新殖民事件的遗传特征，以及将孤立种群联系起来的历史基因流。我们的遗传分析显示 M. guttatus 具有高度分散性，并维持具有高种群内变异的大型复合种群。这种高度的多样性和分散性混淆了遗传结构的推断，