Changes in flowering phenology in response to warming are constrained by community interactions

Background/Question/Methods

The flowering and fruiting phenology of plants is sensitive to climatic cues, so that changes in temperature and moisture levels result in changes in the timing of reproductive events. Changes in the timing of phenological events have therefore been used as important indicator of changes in global climate. Most observational and experimental studies of the relationship between temperature and the timing of phenological events focus on populations of single species, and find evidence for advances in the timing of flowering and fruiting. However, such studies may miss important interactions between temperature and the competitive environment a species faces. Although temporal advances might be predicted from such studies, species may be constrained in their ability to advance by species occupying earlier temporal niches. We examine the relationship between plant growth and flowering in a community context, relating species fitness to competition for resources, growth rate, and flowering time, which are functions of the abiotic and biotic environment. Using a simulation approach, we test how coupling the timing of life history events with competitive interactions can alter expectations for phenological shifts.

Results/Conclusions

Timing of species’ flowering is determined by growth rate and allocation of resources to reproduction, which relies on abiotic cues such as temperature and photoperiod. Competitive interactions between species limit the availability of resources for growth and development; if changes in the growing season due to warming temperatures increase overlap among species, phenological advances may be less than expected. Species fitness is determined by the intersection of growth rate and the timing and length of flowering. Other species can gain competitive advantages from changes in temperature, for example, if they exhibit plasticity in temperature and photoperiod-dependent reactions, or have flexible cues for flowering. Our results suggest that importance of considering the biotic environment a species experiences, and the interaction between abiotic and biotic factors, in order to understand the expected changes in phenology a community may experience.