Ant thermal tolerances under climate, land cover and land use change

Abstract

Thermal stress is a key issue for species dominant within ecosystems especially those that carry out key ecosystem service roles. When assessing the impacts of climate change it is critical to assess its biotic impacts relative to other anthropogenic changes to landscapes including the reduction of native vegetation cover, landscape fragmentation and changes in land use intensity. Here we integrate the observed phenotypic plasticity of the dominant and ubiqitous meat ant Iridomyrmex purpureus in critical thermal limits across altitudinal, land cover and land use gradients to: (i) predict the adaptive capacity of a key terrestrial ecosystem service provider to changes in climate, land cover and land use, and (ii) assess the ability of multiple use landscapes to confer maximum resilience to terrestrial biodiversity in the face of a changing climate. The research was carried out along a 270km aridity gradient spanning 840m in altitude in northern New South Wales, Australia. When we assessed critical thermal maximum temperatures (CTmax) of meat ants in relation to the environmental variables, and within the model we had critical thermal minimums of meat ants (CTmin) as a random slope and as a fixed effect we detected a negative aridity effect on CTmax, a negative effect of land use intensity, and no overall correlation between CTmax and CTmin. We also found a negative relationship with warming tolerance of I. purpureus and landscape aridity. In conclusion, we expect to see a reduction in the physiological resilience of I. purpureus as land use intensity increases and as the climate becomes more arid. Meat ants are key ecosystem engineers and as they are put under more stress, wider ecological implications may occur if populations decline or disappear.