Disentangling resource acquisition from interspecific behavioral aggression to understand the ecological dominance of a common, widespread temperate forest ant

Abstract

Ant communities are structured, in part, by competition between related and unrelated ant species for territories and food resources. In eastern deciduous forests of the United States, a single ant genus (Aphaenogaster) appears ecologically dominant with high abundance and opportunistic foraging. However, Aphaenogaster ants are not particularly behaviorally aggressive toward co-occurring ants, making it unclear as to how they might sustain dominance. We offered myrmecochorous seeds and termite carrion at bait stations and quantified ant aggression, food selection and recruitment. We conducted the experiments throughout the natural seed-release window to determine how the abundance of low- and high-quality food items impacted behavior. We found evidence that Aphaenogaster ants dominate the retrieval of both seeds and insect carrion (dead termites). Aphaenogaster foraging dominance did not appear driven by superior fighting or recruitment abilities but simply by having more foragers on the ground, essentially achieving control of different types of food resources through numerical dominance. Moreover, though they are the dominant effective seed dispersers in the system, A. picea exhibited a much greater affinity for termites than seeds, and the desirability of termites decreased in the presence of seeds. Overall, our results suggest that high numbers of foragers—as opposed to aggressive territoriality—can be an effective ecological strategy for sustaining ecological dominance through resource acquisition.