Structure of complex networks and the role of spatial variations and abundance in plant-ant interactions

Abstract

The structural organization of mutualism networks provides insights into processes shaping biodiversity. Understanding the mechanisms that shape this organization is essential for us to understand the ecological and evolutionary dynamics of the interacting species. Recent studies have suggested that species abundance is one of the most fundamental criteria shaping mutualistic networks. However, the role of species abundance on mutualistic networks is still unclear. Moreover, only recently has the spatial effect been incorporated as a mechanism structuring mutualistic networks. In this work I studied plants with extrafloral nectaries and associated ants to show that the natural abundance of ants on vegetation explained just a part of the frequency of mutualistic interactions and that it is independent of ant species compositions. In addition, the generalist core of these networks interacts more among themselves than expected by their abundances. This generalist core was formed by competitively superior ants that have behavioral and ecophysiological traits to use liquid food and are that exclude other species from the same resource. I also showed that even the fact that ant and plant composition of networks changes over space, the generalist core species and the topological structure of networks remain unaltered. This finding indicates that independently of local and landscape environmental factors the nonrandom pattern of community organization is not changed. Such generalist core conformation being stable over space and time could have serious implications on coevolutionary process of the system. In short, contributing thus to our understanding of the maintenance of biodiversity.