Introduction / Background / Justification

Habitat loss is one the greatest threat to biodiversity with pervasive effects on species diversity, which may generate cascading effects on ecological processes, such as seed dispersal. Thus, understanding how habitat loss affects seed dispersal is fundamental for the conservation and recovery of human-modified landscapes.

Objective(s)/Hypothesis(es)

We gathered a robust database of frugivorous birds and mammals across the Brazilian Atlantic Forest to evaluate the effects of landscape-scale forest loss on richness and species occurrence of both groups. We also used a database of 25 bird-seed dispersal networks distributed across the whole Brazilian Atlantic Forest to understand how landscape-scale habitat loss shapes network structure. Finally, we performed removal experiments in a large-seeded species to evaluate the role of mammals on seed dispersal.

Results

In 153 forest fragments we found 96 frugivorous birds and in 220 forest fragments 18 frugivorous mammals. We found negative effects of forest loss on frugivorous birds and mammal richness and occurrence. Particularly, forest loss has pervasive effects on network structure decreasing the number of links, the number of interactions, and the connectance. In contrast, nestedness increases with habitat loss. Habitat loss also promotes changes in species interaction, shifting the species playing central roles in network organization or contributing to indirect effects. Lastly, the seed removal was directly affected by forest loss but not by changes in mammal assemblage.

Implications/Conclusions

Our results unveil the widespread effect of habitat loss on frugivore assemblages. However, we add evidence that the pervasive effects on biodiversity also proliferate on a key ecological process – seed dispersal. Thus, we suggest that increasing the amount of landscape-scale forest cover in the Atlantic forest is of paramount importance to sustain frugivorous birds and mammals, but also the ecological process they perform. Our approach enables the identification of multiple drivers influencing seed dispersal with several implications for the regeneration and restoration of human-modified landscapes.