An Epiphytic Ant-Plant Mutualism Structures Arboreal Ant Communities

Arboreal ant communities are primarily structured by interactions among ant species, food availability, and physical structures within the environment. Epiphytes are a common feature of tropical forests that can provide ants with both food and nesting space.To date, little work has examined what role epiphytic ant-plants play in structuring arboreal ant communities. We surveyed ant species inhabiting the Australian epiphytic ant-plant Myrmecodia beccarii Hook.f. (Gentianales: Rubiaceae) and how arboreal ant communities are structured in relation to M. beccarii presence on trees. Myrmecodia beccarii was inhabited by the ant Philidris cordata Smith, F. (Hymenoptera: Formicidae) on the majority of Melaleuca viridiflora Sol. Ex Gaertn. (Myrtales: Myrtaceae) trees with ant-occupied ant-plants at our two sites. Dominant arboreal ant species at both study sites exhibited discrete, nonoverlapping distributions, and C-score analysis detected an ant mosaic at one site.The distribution of P. cordata was limited by the distribution of ant-plants for both sites. Philidris cordata dominance on trees was also determined by the presence of M. beccarii occupied by P. cordata at both sites. We suggest that by providing P. cordata with nesting space M. beccarii plays a role in structuring these arboreal ant communities.