Effects of microclimate and species identity on body temperature and thermal tolerance of ants (Hymenoptera: Formicidae)

Abstract

An increase in temperature as a result of anthropogenic climate change is likely to have a significant impact on ground foraging ants, with species closer to the tropics thought to be at greater risk. However, the use of broad scale climate data rather than data from the microclimates ants inhabit brings into question these estimates. This study assesses the effect of microclimate on the body temperature of the dominant meat ant, 'Iridomyrmex purpureus' (Smith, 1858), and the large bull ant 'Myrmecia brevinoda' (Forel, 1910). The body temperature of these ants was recorded on the woodland floor and on the surface of a nearby log. No significant difference in body temperature was detected between the two species or between microclimates. However, a significant interaction between season and species was detected with post hoc analysis showing that the body temperature of M. brevinoda was higher than that of 'I. purpureus' in summer but lower in winter. In addition, the CTmin and CTmax of nine ant species found in Armidale were determined and their warming tolerance calculated. The ants displayed a wide range of thermal tolerances with 'Aphaenogaster longiceps' (Smith, 1858) having the highest CTmax of 48.52°C and Camponotus consobrinus (Erichson, 1842), which had the lowest CTmin of 0.11°C. The body temperatures recorded for deceased 'I. purpureus' and 'M. brevinoda' exposed to the sun exceeded their thermal tolerances, suggesting that these species utilise behavioural or physiological traits not present in deceased ant to regulate body temperature.