PREMISE The timing of germination has profound impacts on fitness, population dynamics, and species ranges. Many plants have evolved responses to seasonal environmental cues to time germination with favorable conditions; these responses interact with temporal variation in local climate to drive the seasonal climate niche and may reflect local adaptation. Here, we examined germination responses to temperature cues in Streptanthus tortuosus populations across an elevational gradient. METHODS Using common garden experiments, we evaluated differences among populations in response to cold stratification (chilling) and germination temperature and related them to observed germination phenology in the field. We then explored how these responses relate to past climate at each site and the implications of those patterns under future climate change. RESULTS Populations from high elevations had stronger stratification requirements for germination and narrower temperature ranges for germination without stratification. Differences in germination responses corresponded with elevation and variability in seasonal temperature and precipitation across populations. Further, they corresponded with germination phenology in the field; low-elevation populations germinated in the fall without chilling, whereas high-elevation populations germinated after winter chilling and snowmelt in spring and summer. Climate-change forecasts indicate increasing temperatures and decreasing snowpack, which will likely alter germination cues and timing, particularly for high-elevation populations. CONCLUSIONS The seasonal germination niche for S. tortuosus is highly influenced by temperature and varies across the elevational gradient. Climate change will likely affect germination timing, which may cascade to influence trait expression, fitness, and population persistence.

中文翻译：

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海拔梯度上季节性发芽生态位的变化：发芽提示在当前和未来气候中的作用

前提 发芽时间对适应度、种群动态和物种范围有着深远的影响。许多植物已经进化出对季节性环境线索的反应，以便在有利条件下定时发芽；这些响应与当地气候的时间变化相互作用，以驱动季节性气候生态位，并可能反映当地的适应性。在这里，我们检查了跨越海拔梯度的 Streptanthus tortuosus 种群对温度线索的发芽反应。方法使用常见的花园实验，我们评估了种群对冷分层（寒冷）和发芽温度的反应差异，并将它们与观察到的田间发芽物候相关。然后，我们探讨了这些响应如何与每个站点过去的气候相关，以及这些模式在未来气候变化下的影响。结果高海拔种群对发芽的分层要求较强，不分层的发芽温度范围较窄。发芽反应的差异与不同种群的季节性温度和降水的海拔和变异性相对应。此外，它们与该领域的萌发物候学相对应；低海拔种群在没有寒冷的秋季萌发，而高海拔种群则在春夏冬季寒冷融雪后萌发。气候变化预测表明气温升高和积雪减少，这可能会改变发芽线索和时间，特别是对于高海拔人群。结论 S. 的季节性发芽生态位。tortuosus 受温度影响很大，并且随海拔梯度变化。气候变化可能会影响发芽时间，这可能会影响性状表达、适应性和种群持久性。