Aim To assess the geographical variation in the relative importance of vertebrate-dispersed species and its main subsyndromes (bird and mammal-dispersal) in woody communities, and to evaluate the influence of location (latitude, longitude and altitude) and climatic factors on the observed trends.
Location 135 communities in the coast of the Atlantic rain forest, SE Brazil.
Methods We collected data on dispersal modes for 2229 woody species (trees and shrubs). By combining the species x site with the species x trait matrices, we obtained the percentages of vertebrate-dispersed (endozoochory), ornitochory, mastozoochory and the mean fruit diameter of the woody communities. We used Spearman’s rank correlations to assess bivariate relationships among variables. Subsequently, we performed paired t-tests to verify if variations in dispersal modes and mean fruit diameter were influenced by altitude or temperature. Then, we applied multiple linear regressions to evaluate the effect of the geographic and climatic variables on variation across communities in the frequency of dispersal modes and mean fruit diameter.
Results We found no consistent latitudinal or longitudinal trend in the fraction of vertebrate-dispersed species, neither bird- or mammal-dispersed fruits along the Atlantic rain forest. The percentage of vertebrate-dispersed fruit species was affected chiefly by annual mean rainfall, increasing in moister sites. Woody communities located at higher altitudes had a higher percentage of bird-dispersed species. Even when sites with identical values of annual mean temperature were compared, altitude had a positive effect on ornitochory. On the other hand, we found a higher percentage of mammal-dispersed species in warmer sites. This trend was consistent even when sites at the same 100 m-altitudinal belts were contrasted. Fruit diameter was clearly related to altitude, decreasing at higher elevations.
Main conclusions This is the first analysis of a large dataset on dispersal syndromes in woody plant communities in tropical rain forests. Our findings support to the hypothesis that (1) large-scale geographic variation in fleshy fruit production is mainly driven by moist conditions and relatively independent of geographic location effects, (2) we fail to support the hypothesis that vertebrate-dispersed syndromes is higher at lower elevations, the elevational trends being specific of dispersal mode, (3) large-scale trends in fruit size correspond to geographic variation in the relative importance of mammal- and bird-dispersal at the community level.

Figure: Distribution of the 135 woody plant communities along the coastal Atlantic rain forest, Brazil. Circle size represents the proportion of vertebrate-dispersed species at each locality.