Flowering phenology is critical for plant fitness due to both abiotic and biotic drivers of reproductive success. On the abiotic side, an individual’s flowering time can influence the potential for frost damage and the soil moisture available for seed development. In terms of the biotic drivers, relative differences in blooming time may impact pollinator visitation rates and availability of pollen donors. However, it is still unclear how individual flowering time and drivers of reproduction impact plant fitness for phenologically distinct species. In this study, we analyzed the impact of relative differences in flowering time on the fecundity of individuals within a population. We collected floral phenology and seed set data for individuals of three subalpine plant species (Mertensia fusiformis, Delphinium nuttallianum, Potentilla pulcherrima) in the Colorado Rocky Mountains. To address the abiotic and biotic drivers of reproduction, we calculated changes in soil moisture, included the density of conspecific individuals, and conducted a pollen limitation experiment to isolate pollination function. Additionally, we accelerated snowmelt to simulate the variability of blooming time caused by climate change. Our statistical models assessed the effects of relative blooming time, soil moisture, conspecific flower density, and pollination treatment on individual fecundity for the three species.
Results/Conclusions
We did not detect an effect of flowering time on seed set for any of the three focal species. This is despite artificially creating greater variability in flowering time and considerable variation in individual seed set. There was no evidence for pollen limitation. The rate of soil moisture loss over the season may have limited seed set in Mertensia and Potentilla. Despite the potential impacts of floral phenology on plant fitness, we found that flowering time did not have strong fitness effects. We found no evidence for phenological mismatches between plants and pollinators that may reduce plant seed for the focal species in this system. This suggests that some species could be more resilient to potential changes in floral phenology.