Plant shade enhances thermoregulation of internal environments in Trinervitermes trinervoides mounds.

Abstract

Microhabitats may be crucial in buffering organisms from temperature extremes, particularly given increases in maximum temperature associated with global climate change. For example, thermoregulation in termite mounds is influenced by prevailing ambient conditions, and plant canopies may reduce external temperatures, in turn lowering internal temperatures. This buffering may be crucial during heat waves. Whether this happens, and to what extent, remains equivocal, however. We tracked internal temperatures in eight inhabited and six uninhabited Trinervitermes trinervoides mounds, half of each group of which were shaded by vegetation. T. trinervoides seek to maintain internal mound temperatures at c. 20 ◦C in winter and c. 30 ◦C in summer. Temperatures were logged for 72 h in winter, and again in summer. Internal temperatures of uninhabited mounds mirrored those of external temperatures, with temperatures varying by c. 15 ◦C, although shading was associated with some buffering of internal temperatures. Internal temperatures within inhabited mounds were far less variable, varying by c. 6 ◦C over the course of our study. In summer, exposed inhabited mounds maintained temperatures c. 29.5 ◦C, whilst shaded inhabited mounds were c. 27.5 ◦C. In winter, mean internal temperatures of exposed and shaded inhabited mounds were very similar, at 21.8 and 22.0 ◦C, respectively. Internal mound temperature varied significantly with external (ambient) temperature, mound activity, temperature, shading, and to a small extent, mound volume. The buffering effect of shade was evident in summer (c. 2 ◦C) but not in winter, suggesting that the benefit of such temperature modulation may be most important when ambient temperatures reach heat extremes, e.g. during heat waves.