Co-fruiting plant species share similar fruit and seed traits while phylogenetic patterns vary through time

Abstract

Co-fruiting plant species are subject to a variety of biotic and abiotic processes that may influence patterns of fruiting phenology and the functional and phylogenetic diversity of co-fruiting taxa in a community. Understanding the seasonal patterns of functional and phylogenetic diversity of fruiting in a community will shed new light on potential mechanisms structuring plant communities. Using rain forest trees in south-eastern Madagascar as our system, we predicted there would be clustering of fruit and seed traits and phylogenetic relationships among co-fruiting species because plants are vying for seed-dispersal services from a limited set of generalist frugivore taxa. We also predicted that seasonal variations in rainfall would mediate fluctuations in functional trait and phylogenetic diversity of co-fruiting assemblages. Despite fluctuating patterns in their functional trait diversity over time, co-fruiting assemblages displayed consistent clustering of fruit/seed traits across time. Phylogenetic diversity was not clustered overall, but fluctuated non-randomly in time, between clustered and overdispersed, such that strong shifts in rainfall were associated with the co-fruiting of more closely related species. Synthesis. We suggest that it may be more beneficial for co-fruiting plant species to share similar fruit and seed traits than to diversify traits, when they rely on a comparatively small set of generalist frugivorous taxa for seed dispersal. Results also demonstrate that rainfall-driven environmental filtering may cause seasonal fluctuations in the phylogenetic patterns of phenology in a community. Results highlight the importance of a temporal context in examining structural patterns of communities.