Finding its place in a competitive ant community: leaf fidelity of Camponotus sericeus

Summary.

Many species of ground nesting ants regularly visit extrafloral nectaries (EFNs) of the savannah tree Pseudocedrela kotschyi. The distribution of ants on the plants is mosaic-like, i.e. stable and predictable with different ant species dominating neighbouring trees. In order to examine whether foraging behaviour may influence the structure of these ant communities, we investigated individual foraging behaviour of Camponotus sericeus, the ant species with highest incidence on P. kotschyi trees in the study area. Foragers of C. sericeus continuously visited EFNs on the leafs of P. kotschyi during their diurnal activity period. Individually marked foragers showed a pronounced fidelity for individual plants and particular leaves. Ant individuals returned to the same plants over a three week period at least. They persistently focused foraging on the same leaves (about three per ant). Null model analysis of ant distribution revealed that ants partitioned their host plant. Co-occurrence on the same leaves was significantly lower than could be expected by chance for most trees studied. Foraging was not oriented towards the plants growing closest to the nest but more distantly growing plants were considerably used. Choice of plants could therefore be influenced by plant quality or by presence of other, competing ant species. The study is the first to show leaf fidelity caused by EFNs and micro-site fidelity within the context of species rich ant communities. It considers the resulting systematic, partitioned use of individual plants as important factor supporting the formation of a mosaic-like ant distribution on plants.