Searching for keystone plant resources in fruit-frugivore interaction networks across the Neotropics

摘要

Identifying keystone plant resources (KPR) is a contentious issue in ecology and conservation. Despite recent advances provided by mutualistic networks, we still lack studies addressing large-scale identification of keystone plants. We developed a novel quantitative framework for the large-scale identification of KPR that combines centrality and effects of simulated removals on networks properties. We built a database with 38 fruit-frugivore networks comprising 6,180 pairwise interactions from Neotropical forest and non-forest ecosystems ranging from sea level to 2,500 m a.s.l.. Effects of random removal simulations and removal of keystone taxa candidates on nestedness, modularity and niche overlap were assessed. Furthermore, we tested whether changes in network descriptors responded to both latitudinal and elevational gradients. From a total of 373 genera on networks, only species in six genera were ranked as keystone candidates. The simulated removal of species in Miconia (Melastomataceae), Cecropia (Urticaceae) and Byrsonima (Malpighiaceae) led to significant changes in nestedness, modularity and niche overlap, suggesting that these plants play important roles in maintaining the structure of Neotropical fruit-frugivore interaction networks, regardless of latitude or elevation. Our results confirm the keystone role of previously recognized taxa, recognize overlooked ones, providing support for their role at a biogeographical scale, and partially challenge taxa traditionally identified as keystone resources for frugivores. Our study has implications for conservation and restoration of Neotropical ecosystems and provides a new framework for large-scale identification of keystones in other types of ecological networks.