The timing of life history events in many plant species is determined by environmental stimuli, such as the timing of snow melt, changes in soil and air temperature, and the timing of canopy closure. Many of these conditions are shifting from their historical patterns with global warming. A standing challenge in ecology is to determine how the phenological shifts of tightly interacting species – such as plants and their pollinators – will influence their joint response to climate change. The objective of our study is to document the natural environmental and phenological patterns in a community of early spring wildflowers, and to assess the role of pollinator-mediated interactions in determining plant reproductive success. During the spring flowering seasons of 2011 and 2012, we quantified the relationships between air temperature, soil temperature, canopy development, and co-flowering plant phenology with the flowering period of the dominant spring ephemeral, Claytonia virginica (Spring Beauty), at the Ross Biological Reserve (Tippecanoe County, IN). In addition, we conducted a pollen supplementation experiment to test the hypothesis that seed production in C. virginica is limited by pollinator activity.
Results/Conclusions
C. virginica began to flower earlier in plots with a higher average air temperature, and completed its life cycle later in plots with a denser canopy cover. We also observed lower seedset and vegetative biomass in C. virginica plants that were surrounded by a more diverse co-flowering community. Finally, excluding pollinators led to a drastic reduction in seedset in C. virginica, but providing supplemental pollen did not increase seed production. Thus, pollinators are critical to C. virginica reproductive output, but are not the limiting factor for seed production in these populations. Collectively, our results indicate that climate-dependent environmental cues critically influence flowering phenology in C. virginica and that seedset in this species is limited by resources, rather than pollinator availability.