Temporal advances in the peak and end of flowering in Streptanthus tortuosus
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Abstract
Climate change is causing shifts in the phenology (timing of life events) of many organisms with consequences such as changes in species interactions and community composition. Owing to the large elevational and latitudinal gradients in its distribution, the native California wildflower, Streptanthus tortuosus (shieldplant) is a great model organism for studying the impacts of climate change. Few studies have looked at temporal shifts in the onset, peak, and end of flowering. Herbarium specimens and local historical climate data were used to make inferences about the temporal shifts of flowering phenology and the impacts of rising mean annual temperature and minimum monthly temperature on flowering phenology. Across the 114 years (1894- 2010) sampled, low elevation specimens (up to 1000 m) were the most sensitive to phenological shifts with their peak flowering advancing by 19 days. The end of flowering in low elevation plants advanced by 17 days. Furthermore, the data demonstrate that increasing temperatures correlated with earlier flowering times for all specimens, particularly at low elevations. Plants at higher elevations displayed smaller shifts in flowering timings.
Taken together, these results suggest that climate change is likely causing shifts in the reproductive phenology of S. tortuosus. Understanding these impacts will enable us to better understand and predict the plant’s ability to adapt and persist in California as it faces new and increasingly variable environmental conditions in the future.