Phenology of growth and reproduction is shifting in many species as a result of recent climate change. Timing of growth and reproduction are often critical for population persistence; therefore, phenological shifts may have detrimental effects on population dynamics. Moreover, interacting species are not shifting phenologies in the same magnitude and direction, which can result in asynchronies in interactions and potential changes in facilitative and competitive interactions.
I used experiments and observational data to examine the relationship between flowering phenology and inter- and intraspecific competition in a subalpine plant community in the Rocky Mountains, Colorado, USA. Claytonia lanceolata (Montiaceae) and Mertensia fusiformis (Boraginaceae) are co-flowering species that have been increasing in temporal overlap since 1974 as a result of earlier snowmelt. To assess how phenology affects plant-plant interactions, I manipulated neighbor density of both species in 2016. The following year, I returned and censused growth, reproduction, survival, and phenology.
Results/Conclusions
In 2017, I found that later flowering C. lanceolata produce more fruits, except when M. fusiformis is present as a neighbor. These results suggest that increased overlap with earlier snowmelt may lead to lower reproductive rates in C. lanceolata if these species are competing. Overall, neighbors increase survival of M. fusiformis, and potentially more overlap may increase population growth rate in this species. These data are the first step towards a broader understanding of the ecological consequences of shifting phenologies in this subalpine plant community.