Aridity and land use negatively influencea dominant species' upper critical thermal limits

Abstract

Understanding the physiological tolerances of ectotherms, such as thermal limits, is important in predicting biotic responses to climate change. However, it is even more important to examine these impacts alongside those from other landscape changes: such as the reduction of native vegetation cover, landscape fragmentation and changes in land use intensity (LUI). Here, we integrate the observed thermal limits of the dominant and ubiquitous meat ant Iridomyrmex purpureus across climate (aridity), land cover and land use gradients spanning 270 km in length and 840 m in altitude across northern New South Wales, Australia. Meat ants were chosen for study as they are ecosystem engineers and changes in their populations may result in a cascade of changes in the populations of other species. When we assessed critical thermal maximum temperatures (CTmax) of meat ants in relation to the environmental gradients we found little influence of climate (aridity) but that CTmax decreased as LUI increased. We found no overall correlation between CTmax and CTmin. We did however find that tolerance to warming was lower for ants sampled from more arid locations. Our findings suggest that as LUI and aridification increase, the physiological resilience of I. purpureus will decline. A reduction in physiological resilience may lead to a reduction in the ecosystem service provision that these populations provide throughout their distribution.

Critical thermal limits in ants and their implications under climate change

“…Maximum monthly temperatures were positively correlated with species CT min but not with species CT max . Finally, Andrew et al (2019) studied thermal tolerance in Iridomyrmex purpureus populations along an aridity gradient, finding a weak increase in both CT max and CT min with increasing aridity.…”

Effects of increasing aridity and chronic anthropogenic disturbance on seed dispersal by ants in Brazilian Caatinga

“…Large ant species are especially sensitive to disturbance (Gibb et al., ; Leal, Andersen, & Leal, ), and this can result in severe reductions in the quality of seed dispersal services in disturbed habitats (Almeida et al., ; Gove, Majer, & Dunn, ; Leal, Andersen, & Leal, ; Ness, Bronstein, Andersen, & Holland, ). Although smaller insects are considered more sensitive to high temperatures through desiccation (Baudier, Mudd, Erickson, & O'Donnell, ; Kühsel, Brückner, Schmelzle, Heethoff, & Blüthgen, ), recent studies have found that the most sensitive ants to climate change are in fact the largest (Andrew, Miller, Hall, Hemmings, & Oliver, ; Gibb et al., ). This might be because large ants require more resources and take longer to mature, thus reducing their adaptive capacity (Gibb et al., ; McCain & King, ; Savage, Gillooly, Brown, West, & Charnov, ).…”

Water-seeking behavior among terrestrial arthropods and mollusks in a cool mesic region: Spatial and temporal patterns

“…Apart from body size, another organismal trait commonly seen in mesic-adapted arthropods is that they have thinner, more permeable cuticles with fewer hydrocarbons [1,50,51]. Evolutionary adaptations to environmental conditions can cause more xeric-adapted "water conserver" species to be present in cities and more mesic-adapted "water seeker" species to be present in undeveloped locations [33,48,49,[52][53][54][55]. Thus, although terrestrial arthropods in mesic regions (and cooler sites) may infrequently experience water limitation, they may be more greatly affected when droughts or heatwaves occur (hypothesized in McCluney [33]).…”