The co-assembly of tropical plant communities and their vertebrate seed dispersers

Background/Question/Methods

We examined communities of birds, primates and trees in protected areas across Uganda. Our objectives were to (1) evaluate the relative importance of dispersal limitation and species sorting along environmental gradients in structuring these communities, (2) determine if dispersal mode influences plant community composition, and (3) assess whether trees dispersed by primates, which were strongly dispersal-limited, were more dispersal limited than trees dispersed by birds, which were not dispersal limited. We conducted partial Mantel tests to investigate correlations between (a) community similarity and ecological distance while controlling for geographical distance and (b) community similarity and geographical distance while controlling for ecological distance.

Results/Conclusions

We found that dispersal limitation strongly structures communities of primates whereas species sorting strongly structures communities of birds and trees. Upon closer analysis of tree dispersal modes, we found that wind-dispersed trees also exhibit evidence of significant dispersal limitation but that trees dispersed by animals and other methods do not. We also found consistent trends that primate fruit trees exhibited greater dispersal limitation than bird fruit trees across three fruit color dispersal syndromes. Taken together, our results suggest that the dispersal abilities of primary consumers affect the distribution of primary producers at a macro-ecological scale.