Department of Evolution and Ecology, University of California-Davis, Davis, CA, 95616, USA.
Center for Population Biology, University of California-Davis, Davis, CA, USA.
Am J Bot. 2020 Feb;107(2):350-363. doi: 10.1002/ajb2.1425. Epub 2020 Feb 13.
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.
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.
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.
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.
萌发的时间对适合度、种群动态和物种分布范围有深远的影响。许多植物已经进化出对季节性环境线索的反应，以便将萌发时间与有利条件相匹配；这些反应与当地气候的时间变化相互作用，推动季节性气候生态位，并可能反映出当地的适应。在这里，我们研究了扭果苣属（Streptanthus tortuosus）种群在海拔梯度上对温度线索的萌发反应。
通过使用共同的花园实验，我们评估了不同种群对冷层积（冷藏）和萌发温度的反应差异，并将这些反应与野外观察到的萌发物候学相关联。然后，我们探讨了这些反应与每个地点过去气候的关系，以及这些模式在未来气候变化下的影响。
高海拔地区的种群对萌发有更强的分层要求，且无分层萌发的温度范围较窄。萌发反应的差异与种群间的海拔和季节性温度及降水变化相吻合。此外，它们与野外的萌发物候学相吻合；低海拔地区的种群在秋季无需冷藏即可萌发，而高海拔地区的种群则在冬季冷藏和春夏季融雪后萌发。气候变化预测表明，温度升高和积雪减少，这可能会改变萌发线索和时间，特别是对高海拔地区的种群。
扭果苣属的季节性萌发生态位受温度影响很大，且在海拔梯度上有所变化。气候变化可能会影响萌发时间，这可能会影响特征表达、适合度和种群生存。
