The global distribution of frugivory in birds

To examine patterns of avian frugivory across clades, geography and environments. Global, including all six major biogeographical realms (Afrotropics, Australasia, Indo-Malaya, Nearctic, Neotropics and Palaearctic). First, we examine the taxonomic distribution of avian frugivory within orders and families. Second we evaluate, with traditional and spatial regression approaches, the geographical patterns of frugivore species richness and proportion. Third, we test the potential of contemporary climate (water-energy, productivity, seasonality), habitat heterogeneity (topography, habitat diversity) and biogeographical history (captured by realm membership) to explain geographical patterns of avian frugivory. Most frugivorous birds (50%) are found within the perching birds (Passeriformes), but the woodpeckers and allies (Piciformes), parrots (Psittaciformes) and pigeons (Columbiformes) also contain a significant number of frugivorous species (9-15%). Frugivore richness is highest in the Neotropics, but peaks in overall bird diversity in the Himalayan foothills, the East African mountains and in some areas of Brazil and Bolivia are not reflected by frugivores. Current climate explains more variance in species richness and proportion of frugivores than of non-frugivores whereas it is the opposite for habitat heterogeneity. Actual evapotranspiration (AET) emerges as the best single climatic predictor variable of avian frugivory. Significant differences in frugivore richness and proportion between select biogeographical regions remain after differences in environment (i.e. AET) are accounted for. We present evidence that both environmental and historical constraints influence global patterns of avian frugivory. Whereas water-energy dynamics possibly constrain frugivore distribution via indirect effects on food plants, regional differences in avian frugivory most likely reflect historical contingencies related to the evolutionary history of fleshy fruited plant taxa, niche conservatism and past climate change. Overall our results support an important role of co-diversification and environmental constraints on regional assembly over macroevolutionary time-scales.