The process of adaptation can be highly dependent upon historical and contemporary factors, especially in environmentally and topographically complex regions affected by Pleistocene glaciations. Here, we investigate Hilaria jamesii (Poaceae), a dryland C₄ graminoid, to test how patterns of adaptive genetic variation are linked to its glacial and post‐glacial history. We show that the species persisted in a single, southern refugium during the last glacial period and subsequently migrated throughout its current distribution concurrent with post‐glacial warming. The species’ putative adaptive genetic variation correlates with climatic gradients (e.g. monsoon precipitation and mean diurnal temperature range) that covary with the species’ probable route of demographic expansion. The short timescale and multiple climatic dimensions of adaptation imply that natural selection acted primarily upon standing genetic variation. These findings suggest that restoration and conservation practices should prioritize the maintenance of standing genetic variation to ensure that species have the capacity to respond to future environmental changes.

中文翻译：

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当代气候适应的历史背景：美国西南部气候动态和环境复杂的案例研究

适应过程可能高度依赖于历史和当代因素，特别是在受更新世冰川影响的环境和地形复杂的地区。在这里，我们研究了禾本科（禾本科），一种旱地 C₄ 禾本科植物，以测试适应性遗传变异的模式如何与其冰川和冰川后历史相关联。我们表明，该物种在最后一个冰河期持续存在于一个单一的南部避难所中，随后随着冰河后变暖而迁移到其当前的分布区域。该物种假定的适应性遗传变异与气候梯度（例如季风降水和平均昼夜温度范围）相关，后者与该物种可能的人口扩张路线共变。适应的短时间尺度和多个气候维度意味着自然选择主要作用于常设的遗传变异。这些发现表明，恢复和保护实践应优先维护长期遗传变异，以确保物种有能力应对未来的环境变化。