Upper thermal tolerance of tropical and temperate termite species (Isoptera: Rhinotermitidae, Termitidae): a test of the climate variability hypothesis in termites

Extrema in temperature tolerances are a selective factor contributing to variation between populations and species. The climate variability hypothesis (CVH) posits that organisms exposed to a wider range of temperatures are expected to have a wider thermal range. This pattern is common across many taxa. In this study, we investigate how social insects vary in thermal tolerance. We test if social role in termites influences tolerance to temperature maxima, and given ties between social roles and body size, whether it is a primary correlate. Our methods examined upper lethal limit (ULL) and dry weights of five termite species representing two families across four sites in Texas and Costa Rica. With the addition of previously recorded upper heat tolerances in the literature, we conclude that termites follow the CVH and upper heat tolerance is positively correlated with absolute latitude. Our results show a differentiation in heat tolerance by task (collected from foraging site versus from nest) for Nasutitermes corniger soldiers but not workers. In the remaining species, there was no ULL partitioning by caste (soldier versus worker). Body size significantly correlated with ULL with the exception of Cornitermes walkeri, an outlier in both body size and ULL. A better understanding of how termites cope with temperature is important for this essential wood decomposer in a changing climate.