Changes of a mutualistic network over time and its influence on outcomes of interactions

Ecologists and evolutionary biologists have pointed out that plant-animal interactions occur in a community context of complex ecological interactive networks and that the understanding of who interacts with whom in these systems is a key approach to draw valid conclusions about evolutionary process in community ecology. However, despite the numerous studies that describe patterns of ecological interactions in the scientific literature, little is known about the results of interactions involving networks. Here we explored the structural properties of mutualistic network between ants and plants with extrafloral nectaries (EFNs) over time (including the outcomes of interactions. A module plant community was focused on with the most abundant species of a Neotropical Savanna and the effect of interactions in leaf herbivory was examined over two years. The interactions network found was similar to others found in the literature: nestedness and low degree of specialization. This pattern remained over time although there were changes in network connectance. The frequency distribution of degree also varied over time, however, the difference was not significant neither for ants nor to plants. Our results confirm the protective effect of ants (leaf herbivory reduction) on the community of plants bearing EFNs, although there was a variation in the effectiveness of this protection over the two years of study. Our study pointed out that what can be manipulatively experienced in single systems, can also be done to compartments in network interactions providing us with more general and broader vision of the process occurring in the entire community.