The trade-off between thermal tolerance and behavioural dominance in a subtropical South American ant community

Summary

1. The distribution, ecology, and behaviour of ants (Hymenoptera: Formicidae) is profoundly influenced by environmental stress and competition. As in plants, trade-offs in adaptations to these factors are the basis for functional classifications of ant taxa and communities at a global scale.

2. Theory predicts a trade-off between stress tolerance and competitive dominance in both plants and ants. In ants, low temperature is thought to be stressful, so I hypothesized that there would be a positive relationship between temperature and behavioural dominance. I evaluated this relationship in a South American, Chaco ant community.

3 The activity and behaviour of ground-foraging, omnivorous ants were examined at baits in open and closed, forested habitats during different seasons and times of day to characterize the responses of ant taxa to variation in microclimate and competitors.

4. Behaviourally dominant ants were most active at moderately high temperatures, whereas subordinate species were active at extreme temperatures, when they had virtually exclusive access to resources.

5. The patterns presented here and those observed in other studies suggest that there is a general trade-off between behavioural dominance and thermal tolerance in ants. This trade-off creates a linear relationship between temperature use and dominance for ants up to ≈ 35 °C, but extremely high temperatures may also be stressful such that the full relationship is actually unimodal.