Flowering phenology is an important aspect of plant reproductive ecology, and the timing of flowering may be affected by competition from neighbours. Previous work at our field site has demonstrated that higher intraspecific than interspecific competition stabilizes coexistence between plants. Phenological differentiation may be a mechanism that stabilizes coexistence between species. If competition delays or accelerates flowering times this could affect niche and fitness differences and competitive outcomes. To explore whether competition impacts species’ flowering times, we experimentally planted five annual plant species in the field with competition densities at 0, 5, 10, and 15g/m3. We tracked the reproductive phenophases of the plants and compared the timing of first flower and length of total flowering period in 232 plots to determine whether competition density and identity of competitors influenced phenology. To test whether competition-induced changes in phenology influence individual fitness, we selected focal individuals of each species and counted the total number of seeds produced.
Results/Conclusions
Uropappus lindleyi was the first species to flower, beginning on 08 April 2018, and Festuca microstachys was the last species to begin flowering, 16 days later. Preliminary results show that competition significantly accelerated flowering time for two species and significantly lengthened total flowering period for a third. Of these species, results suggest that acceleration of flowering time increases with competition density. However, individuals grown without competitors produced significantly more seeds, having the highest individual fitness. Further analysis on whether shifts in phenology are influenced by identity of competitors will have implications for identifying the role of phenology in species coexistence. Changing climate in California has dramatic consequences for species phenology; a better understanding of how phenological differences influence species coexistence will be critical to predicting the outcome of species interactions.