The Role of Higher Order Interactions in Structuring Competitive Communities: an empirical study in ant communities

Abstract

Understanding the mechanisms which allow for the maintenance of diverse communities is one of the central foci of ecology. Recent work suggests that complex interactions such as trait-mediated indirect interactions (TMIIs), and more generally higher-order interactions, may play an important role in structuring ecological communities. Here we use a well-studied system of arboreal ants in coffee agroecosystems to empirically explore the role of TMII’s in structuring this community. We use, Azteca sericeasur, a dominant arboreal ant which excludes other ants from occupying coffee bushes near the trees where its nest is located. Prior work in the system has established a TMIIs between A. sericeasur and its specialist Pseudacteon spp parasitoids. Furthermore, this TMIIs is far greater on younger nests than older nests. Here we ask how varying strengths of TMIIs /parasitoid pressure influence the community of ants associated with A. sericeasur. For this, we surveyed A. sericeasur nests of varying ages to understand the influence of the parasitoids on the structure of the arboreal and leaf litter ant community in space and through time. At each nest we surveyed the arboreal ants on all the coffee plants that fall within a radius of 8-10 m around the nest. For leaf litter ants, at each nest we traced two linear transects from which we collected six samples of .5 m2 of leaf litter, in total 12 samples per nest. Then, the ants from each sample were extracted using winklers and identified to species and morpho species. Our results show that next to A. sericeasur younger nests the richness of other ants closer to the nest (0-4 m) is higher in comparison to the same distance to older nests where the richness of other ants was lower. Interestingly near old nests the richness of the other ants starts increasing rapidly at 4 m up to 9 m contrary to the richness of the other ants next to young nests where the richness from 2 m to 6 m remains constant. The results from this study show the potential role of the Trait- Mediated Indirect Interactions in structuring competitive communities, since next to younger nests, the richness of ants is higher in comparison to low density of phorids nests. This particular system allows us to determine if the communities of ants is different when we have high TMIIs (high density of phorids) and low TMIIs (low density of phorids).