Meeting Abstract
Climate warming is predicted to have particularly strong effects on tropical organisms. Studies suggest that tropical organisms have evolved to be thermal specialists that routinely experience habitat temperatures close to their physiological limits. Most of this work is theoretical or based on mining physiological data from the literature and temperature data from weather stations. Therefore, many questions remain regarding the precise empirical relationships between the thermal tolerances of tropical organisms and the thermal environments they experience. In this study, we compared the thermal tolerance of individual Atta cephalotes soldier ants inhabiting very different thermal regimes in rain forest and nearby dry forest in Area de Conservacion Guanacaste (ACG), Costa Rica. Thermo-limit respirometry profiles indicated no significant difference in upper thermal tolerance (CTmax) between rain forest and dry forest ants. However, the frequency and magnitude of discontinuous gas exchange patterns were higher in ants collected from the rain forest. Infrared imaging of the nest surface coupled with hourly air and soil surface temperature recordings indicated that only dry forest ants could experience habitat temperatures close to and even beyond the estimated CTmax. These results raise the question of how tropical insects, like ants living in ACG dry forest, will respond to warming. However, in contrast, results for rain forest ants suggest a large safety margin for warming and question the generality of the idea that tropical organisms routinely operate close to their thermal limits.
