Pollinator-mediated facilitation is associated with floral abundance, trait similarity and enhanced community-level fitness

Pollinator-mediated processes (biotic filtering, facilitation or competition) are often inferred by patterns of plant reproductive trait diversity (clustering or evenness of reproductive traits within the community). However, one single pattern can be generated by distinct processes, making difficult to predict the main process of community assembly. Incorporating fitness estimates should improve the link between pattern and process. We investigated patterns of flowering phenology and reproductive traits (floral colour, floral size and anther height) along the season of a pollinator-depauperated and generalized community. We used data on fitness (pollen receipt and number of pollen tubes) to provide a functional link between trait patterns and assembly mechanisms. We also investigated whether the degree of co-flowering depended on the floral abundance and pollination functional group (fly-, bee-, hummingbird-pollinated and generalist species) of the plant species. High floral abundance in the flowering season was associated with low trait diversity in the community. Both features increased fitness at the community level. This indicates that similar species are benefited at periods of high floral abundance, probably due to the joint attraction of generalist pollinators in this pollinator-depauperated community. In general, rare species flowered more synchronously with the community than abundant ones, although distinct patterns emerged depending on the floral trait and pollination functional group. Furthermore, species highly synchronous and possessing similar floral colour in relation to the community had higher fitness indicating that facilitative mechanisms act favouring flowering synchrony and trait similarity. Synthesis.Patterns of flowering synchrony and floral trait similarity indicate pollination facilitation in the studied community. Plants benefited from co-flowering with species possessing similar floral colour via shared pollinator attraction. Thus, we empirically demonstrated some of the predictions of community assembly theory.