Generalist Species Have a Central Role In a Highly Diverse Plant-Frugivore Network

Abstract

Analysis of plant-frugivore interactions provides a quantitative framework for integrating community structure and ecosystem function in terms of how the roles and attributes of individual species contribute to network structure and resilience. In this study, we used centrality metrics to rank and detect the most important species in a mutualistic network of fruit-eating birds and plants in a cloud forest in the Colombian Andes. We identified a central core of ten bird and seven plant species in a network of 135 species that perform dual roles as local hubs and connectors. The birds were mostly large forest frugivores, such as cracids, cotingas, and toucans, which consume fruits of all sizes. The plants were species of intermediate successional stages with small- to medium-sized seeds that persist in mature forest or forest borders (e.g., Miconia, Cecropia, Ficus). We found the resilience of our network depends on super-generalist species, because their elimination makes the network more prone to disassemble than random extinctions, potentially disrupting seed-dispersal processes. At our study site, extirpation of large frugivores has already been documented, and if this continues, the network might collapse despite its high diversity. Our results suggest that generalist species play critical roles in ecosystem function and should be incorporated into conservation and monitoring programs. © 2016 The Association for Tropical Biology and Conservation.