Pollen limitation (PL) is the reduction in the reproductive success due to inadequate pollen deposition in the stigma and a proxy for reduced plant fitness. Although PL for plant reproduction has been widely studied, our understanding of its occurrence and role in community assembly is incipient, especially in the tropics. PL can translate ecological processes that act on the assembly of plant species that share pollinators. The predominance of a process can vary throughout the flowering reflecting the temporal dynamics of the community. Here, we aimed answer what is the main ecological processes acting on the assembly of a community under the perspective of plants’ interactions with pollinators. If facilitation is the main ecological process, we predict reduced PL in response to functional clustering (trait or flowering overlap). However, if competition is predominant, we expect reduced PL with functional evenness (trait and flowering segregation). Moreover, we assessed how the predominance of these processes may vary along the flowering of a focal species depending on the ecological context. For this, we used a community of plants pollinated by hummingbirds. We assessed PL by pollination experiments in the field and measured floral traits and the flowering phenology of the community.
Results/Conclusions
We recorded a positive relationship between plant fitness and flowering synchrony suggesting facilitation as the most important process for this montane plant community. However, for the focal Gesneriaceae species, Nematanthus crassifolius, PL varied along its flowering phenology depending on the ecological context, i.e. number of co-flowering individuals in the community. Although a clear pattern was not detect, the prevalence of competition is suggested based on higher PL with increased number of co-flowering plants in the community at the middle stage of the N. crassifolius flowering. This means a 1.5 to 2 times higher PL compared to at the beginning and the end of the population flowering, when the number of co-flowering individuals at the community level was lower. The results suggest facilitation among plant species that share pollinators in a broader sense for the whole community. However species-specific response may shift depending on the ecological context, especially for long-bloomer species. These results highlight the importance of studying PL at the community level and its relevance for a better understanding of the ecological processes that act on plant community assembly. Thus, the relative importance of each ecological process may shift depending how the community context changes.