Understanding biotic responses to global warming continues to be of the critical issues being assessed by biologists. I will present recent research from my research group on micro- and macro- climatic variation.
Firstly, thermolimit respirometry was used to determine metabolic rate responses and thermal limits of the dominant meat ant, Iridomyrmex purpureus. I tested the hypothesis that local microclimates have a pervasive influence on thermal limits.
Secondly I will address the issue of adapting landscapes for improved insect biodiversity conservation in a changing climate by assessing the importance of additive (main) and synergistic (interaction) effects of land cover and land use with climate. I tested the hypotheses that ant richness (species and genus), abundance and diversity would vary according to land cover and land use intensity but that these effects would vary according to climate. A 1000 m elevation gradient in eastern Australia was used as a proxy for a climate gradient and ant biodiversity was sampled along this gradient from sites with variable land cover and land use.
Firstly, at all the stages of thermolimit respirometry, metabolic rates were independent of microclimate surface temperatures. ‘At high temperatures (>44°C) pre- CTmax the relationships between I. purpureus CTmax values and mass specific metabolic rates for whole ants exhibited a negative slope. The findings suggest that physiological responses of ants may be able to cope with increasing microclimate temperatures, as shown by metabolic rates across the thermolimit continuum, but with most resilience to thermal stress around nest surface temperatures of 42°C.
Secondly we found that higher ant richness (species and genus) and diversity with greater native woody plant canopy cover; and lower species richness with higher cultivation and grazing intensity, bare ground and exotic plant groundcover. Interaction effects revealed: both the positive effects of native plant canopy cover on ant species richness and abundance, and the negative effects of exotic plant groundcover on species richness were greatest at sites with warmer and drier climates. Impacts of climate change on insect biodiversity may be mitigated to some degree through landscape adaptation by increasing woody native vegetation cover and by reducing land use intensity, the cover of exotic vegetation and of bare ground. Importantly, they also provide evidence of synergistic effects suggesting that landscape adaptation may be most effective in areas which are currently warmer and drier, or are projected to become so as a result of climate change.