Rainfall influences plant richness and predicts birds phylogenetic signal in bird-fruit interactions across the globe

Abstract

Interactions between frugivorous birds and plants derive from current ecological contingencies and species’ evolutionary history, yet disentangling the relative role of these drivers in assembling biotic communities is challenging. As species usually inherit functional traits from a common ancestor, the interactions between fruit-eating birds and plants may show strong phylogenetic signals (i.e. closely related bird species share similar plant partners). However, we are still largely unaware of how climatic factors may influence the phylogenetic signals in bird-fruit interactions. Here, we investigated whether higher precipitation and temperature (i.e. higher primary productivity), together with climatic stability (i.e. lower precipitation and temperature seasonality), increase plant richness and promote stronger phylogenetic signals of both birds and plants. We found annual rainfall and temperature stability predicted plant richness. Birds phylogenetic signal was associated with mean annual precipitation, but the phylogenetic signal of plant species was not associated with any climatic predictor. We suggest that higher rainfall facilitates the coexistence among frugivorous birds by providing more fruits, which allows closely related birds to use similar resources. Understanding how ecological and evolutionary contingencies act to shape bird-fruit interactions at large spatial scales may help us predict macroecologial patterns that generate and maintain biodiversity.