The structure of ant–plant ecological networks: Is abundance enough?

Abstract

Knowledge of the mechanisms that shape biodiversity is essential to understand the ecological and evolutionary dynamics of interacting species. Recent studies posit that most of the organization of mutualistic networks is shaped by differences in species abundance among interacting species. In this study, we examined the mutualism involving plants with extrafloral nectaries and their associated ants. We show empirically that the difference in abundance among ants on vegetation partially explains the network structure of mutualistic interactions and that it is independent of ant species compositions: an ant species that is abundant usually interacts with more plant species. Moreover, nested networks are generated by simple variation in ant abundance on foliage. However, in ant-plant mutualistic networks, nestedness was higher than in networks describing the occurrence of ants on plants without a food resource. Additionally, the plant and ant species with the highest number of interactions within these networks interacted more among themselves than expected under the assumption of an abundance-based, random mixing of individuals. We hypothesize that the dominance of these ant species occurs because these ants are able to outcompete other ant species when feeding on extrafloral nectaries and because of the presence of ecophysiological adaptations to utilize liquid food.

The network structure of myrmecophilic interactions

“…An alternative explanation involves interactions occurring randomly between individuals, with probabilities of occurrence being mostly determined by species abundance (Vázquez et al, 2009). However, recent evidence reveals that for ant-EFN networks, some interactions occur more frequently than expected by species abundance, reinforcing the nested structure of the network (Dáttilo et al, 2014b). According to our results, it seems reasonable not to separate EFN and trophobiont interactions when studying resource use by ants and interaction networks in order to fully understand the patterns and dynamics of ant-partner communities.…”

“…These results suggest that species phylogeny may not be the most important factor in partner selection, either for ants or for partners. Partner selection by ants could be driven by other factors not necessarily shared by related species, such as phenology (Rico-Gray et al, 2012), abundance (Chamberlain et al, 2010;Dáttilo et al, 2014b), body size (Chamberlain & Holland, 2009b), ant dominance hierarchies (Dáttilo et al, 2014a) and abiotic factors (Rico-Gray et al, 2012), which have been demonstrated to be good predictors of the structure of ant-EFN interaction networks. Moreover, ant visitation to FN was shown to depend on seasonality (Santos et al, 2014), and the presence of floral barriers and repellents, which were in turn independent of plant phylogeny (Junker et al, 2011).…”

Individual-Based Ant-Plant Networks: Diurnal-Nocturnal Structure and Species-Area Relationship

“…This pattern indicates that within an ant-plant network there is a core of generalist species (those with the most interactions), which interact among themselves, and specialists species (those with fewer interactions) also interacting with the generalist species in cohesive subgroups [9]. Another characteristic of these facultative ant-plant networks is that they do not exhibit a modular pattern of interactions, since there are no groups of ants specialized in feeding on a given group of plants [10], [11]; as previously demonstrated in symbiotic networks involving ants and myrmecophytes [12]. However, despite the importance and increasing knowledge of ant-plant networks at the community level, no study has evaluated how intrapopulation variation in plants can contribute to the organization of the ant species associated to individual EFN-bearing plants.…”

Eucharitid ant-parasitoid affects facultative ant-plant Leea manillensis: top-down effects through three trophic levels

“…Interactions between organisms can be very complex and are often yet unexplored (Dáttilo et al 2014), especially in tropical forests. Within ecosystems, members of different trophic levels are interacting with each other by regulatory forces.…”