Keystone species in seed dispersal networks are mainly determined by dietary specialization

One central issue in Ecology ecology has been the definition and identification of keystone species, i.e., species that are relatively more important than others for maintaining the structure of a community. Several keystone species concepts have been proposed, and network theory has been pointed out recently as a good theoretical framework for this kind of study. We used the network concept of centrality, measured in different ways, as a proxy for different aspects of a species relative importance in seed dispersal networks composed of either frugivorous bats or birds and their food-plants. Centrality was expected to be determined mainly by dietary specialization, and but also by body mass and geographic range size. In Across 15 Neotropical datasets, specialized frugivores were the only species to reach the highest values of centrality. Furthermore, the centrality of those specialized frugivores varied largely within and among networks, whereas that of secondary and opportunistic frugivores was consistently low. A multivariate model showed that centrality was best explained by dietary specialization, and but not by body mass or range size, and that the relationship between centrality and these ecological correlates differed between bat- and bird-fruit networks. Our findings suggest that dietary specialization is key to understand how keystone frugivores emerge in seed dispersal networks. This indicates that, and they also help predict part of the relative importance of a speciesplay a disproportional role for community structure and ecosystem functioningin a mutualistic community, which can be used as a tool in could be important forhas important implications for conservation or restoration programs.