Colony-level mechanisms of thermal tolerance regulation in the ant
Ectatomma ruidum
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 ant 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.