Abundance and size of birds determine the position of the species in plant-frugivore interaction networks in fragmented forests

Abstract

The relationships between frugivorous animals and plants are of vital importance particularly in tropical forests. The way species interact and how they are organized within interaction networks could be determined by their ecological and morphological characteristics. This study evaluates the hypothesis that the topological position of species within an interaction network is determined by their degree of frugivory, body size, and abundance. Thus, we constructed the frugivory network between birds and plants in a rainforest fragment in northwestern Colombia. The position of the species within the network was calculated based on three centrality measures (degree, betweenness, and closeness), and its association with relative abundance, degree of frugivory, and body size of each bird species was evaluated by means of a generalized linear model. We found that the species that were most abundant and had the smallest body size had central positions in the interaction network. This pattern is contrary to what has been observed in pristine forests, where species with large body size are more important for network stability. Our results suggest that forest fragmentation modifies the roles of species within the network structure, in part, due to changes in the makeup of the original frugivore community. The information presented may be useful to evaluate the effects of the loss of species as a result of anthropic actions, with the aim of generating ecosystem restoration strategies.