Earlier spring reduces potential for gene flow via reduced flowering synchrony across an elevational gradient

Premise: One of the best-documented ecological responses to climate warming involves temporal shifts of phenological events. However, we lack an understanding of how phenological responses to climate change vary among populations of the same species. Such variability has the potential to affect flowering synchrony among populations and hence the potential for gene flow.

Methods: To test if an earlier start of the growing season affects the potential for gene flow among populations, we quantified the distributions of flowering times of two spring-flowering plants (Trillium erectum and Erythronium americanum) over six years along an elevation gradient. We developed a novel model-based metric of potential gene flow between pairs of populations to quantify the potential for pollen-mediated gene flow based on flowering phenology.

Results: For both species investigated, earlier onset of spring led to greater separation of peak flowering dates across the elevation gradient. For T. erectu...