Coexistence among relatives at Bodega Marine Reserve: Correlations between flowering phenology, and phylogenetic distance

Background/Question/Methods

Several processes have been invoked to explain coexistence among species -- ecological niche partitioning, reproductive isolation and nearly-neutral dynamics through ecological similarity. Explaining coexistence among close relatives is an added challenge, as they are often similar in stature and fitness, and can occur in similar environments.

Reproductive phenology in plants is important both ecologically, in terms of seed set, and evolutionarily, via reproductive isolation. Phenology may thus contribute to determining community composition. Overlap in flowering time could provide a barrier to establishment if species compete for pollinator services, suffer from pollen swamping, or produce inferior hybrid offspring. Alternatively, overlap in flowering time could lead to facilitation by attracting pollinators or could allow species to take advantage of favorable growing season environments. 

We are interested in the relationship between phylogenetic relatedness and amount of overlap in flowering time between species in a community. We observed floral phenology for one hundred species of flowering, insect-pollinated monocots and dicots at the Bodega Marine Reserve from January to September of 2011. We quantified the flowers, fruits, and buds for individuals of each species at several points over the season to create flowering time curves, providing a more nuanced exploration of overlap. 

Results/Conclusions

Using a Mantel test to test correlation between two distances matrices (phylogenetic distance and overlap in flowering time), we have found significantly less overlap in flowering among closely related species than among more distantly related species (p < 0.05). The amount of overlap between species increased with phylogenetic distance. Using Blomberg’s K-statistic, we found no phylogenetic signal in date of first flower, peak flowering time, or duration of flowering time. These results suggest that for closely related species, overlap in flowering time could be disadvantageous for establishment and species coexistence.