Structural changes over time in individual‐based networks involving a harvester ant, seeds, and invertebrates

Abstract

1. Harvester ants perform important ecological functions, such as seed predation and redistribution of nutrients in the soil, through a complex of ecological interactions. Most studies are static descriptions of network structure, while their temporal organisations and the factors that modulate it have been neglected.2. This study describes the temporal organisation and the influence of climatic variables (e.g. temperature and rainfall) on network structure between a harvester ant species and its food resources (seeds and invertebrates) in the Brazilian savanna over a 1‐year period. In addition, considering the ant–seed networks, the relationship between the size of seeds collected by ants and the distance travelled was examined, as well as how this relationship behaves over time.3. For all network types (ant–seed, ant–invertebrate, and combined) there was great structural variation throughout the year. Among climatic variables, only rainfall influenced the properties of ant–invertebrate networks, presenting a positive influence on diversity of interactions and a negative influence on network specialisation. Finally, this study shows that harvester ants tend to collect larger seeds in the vicinity of the nest (< 5 m) and smaller seeds at greater distances, and this relationship appears to be constant over time.4. This study highlights that ecological networks are useful tools with which to understand the temporal organisation of ecological functions. In addition, climatic changes, mainly in the rainfall regime, may interfere directly in the availability of resources and ultimately in the interactions between harvester ants and their food resources.