Disentangling the architecture of the frugivorous bird-plant interaction networks in a savanna-forest mosaic in the Neotropical savanna

Abstract

In tropical regions, savanna and forest formations that occur adjacently in the landscape often differ in relation to the structure of assemblages of species they harbour. However, it has not yet been evaluated whether the structure of the interaction networks also differs between adjacent heterogeneous environments. Here, we describe and compare the structure of the frugivorous bird-plant interaction networks in a savanna-forest mosaic in the Brazilian savanna. Due to the high diversity of birds and plants in this Neotropical savanna, we expect that most interactions are concentrated in highly connected generalist species, revealing a nested pattern, and that greater vertical stratification propitiates more interactions in forests, which generates differences in the structure of networks between the two environments. We recorded 185 interactions involving 60 species of birds and 42 species of plants. The interactions network in the savanna-forest mosaic was nested and non-modular. Considering the two environments separately, the forest formations network was also nested and not modular and the savanna formations network was neither nested nor modular. This difference in the structure of networks shows the importance of forests for the frugivorous avifauna and the processes of seed dispersal, and the stability of the interactions in heterogeneous environments such as the Brazilian savanna.