How are organized the plant-frugivorous bird interaction networks in a Savanna-Forest mosaic in the Cerrado?

In the tropical regions, savanna and forest formations that occur adjacently in the landscapes may differ in relation as structure of the assemblages. Here, we recorded interactions of frugivory by birds in savannas and forests formations in the Brazilian Cerrado to answer the following questions: (i) How is organized the frugivorous bird-plant network? (ii) Is the structure of the interaction networks different in savannas and forest formations? We conducted the study in a mosaic of savannas and forests in the Serra Azul State Park (15º52’S, 51º16’W) in Mato Grosso State, Brazil. We recorded the frugivory events through linear transects (248 hours of observation) and focal method (36 hours) in 2009-2012. We organized the data as a qualitative matrix to calculate the connectance and the nestedness. We recorded 180 interactions involving 54 species of birds and 41 species of plants, and the connectivity was 8.13%. The bird-plant network was nested (NODF = 21.39; p < 0.001). However, when we considered each independently, we found the network structure to be different in savannas (NODF = 19.84, p = 0.13) and forests (NODF = 26.69, p < 0,001). This difference can be due to the greater availability of resources and vertical stratification in forest formations, allowing alternative routes of interactions. For us, this is an indicative of the importance of forests in the maintenance of interactions in heterogeneous environments such the Cerrado and of more specialized associations in savanna formations, suggesting that this type of environment is more fragile to the loss of interactions.