Abstract
1. Insects spend energy to function in high temperature environments,
and because social insects employ a division of labor, it is likely that
thermal tolerance varies among individuals in the colony, based on the
tasks that they perform.
2. Foraging workers of the Neotropical ant Ectatomma ruidum are
known to show temporal differences in thermal tolerance, with greater
tolerance in hot afternoons, relative to cool mornings.
3. We developed three hypotheses that can account for temporal
differences in thermal tolerance among workers: Thermal Acclimation,
Division of Labor, and Circadian Rhythm.
4. We tested these hypotheses with a pair of experiments that involved
the measurement of thermal persistence of ants at a constant temperature
in time-to-failure assays. The first experiment compared ants with
different behavioral roles in colonies, and the second compared colonies
subjected to thermal manipulations, then iteratively sampled at daily
thermal maxima and minima.
5. We found robust support for the Circadian Rhythm and Thermal
Acclimation Hypotheses, and little support for the Division of Labor
Hypothesis. Colonies of this species integrate multiple mechanisms of
adapting to thermal challenges including time of day, ambient
temperature, and the behavioral context of individual workers.