The role of nest surface temperatures and the brain in influencing ant metabolic rates

Miller

Hemmings

et al. 2018

Preprint

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.

Section: Site Selectionmentioning

confidence: 85%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Miller

Hemmings

et al. 2018

Preprint

“…However, our previous study with S. rubrus found a temperature effect on beetle performance even though the temperatures in the experimental chambers were much lower than the CT max of S. rubrus (Holley & Andrew ), suggesting that it may be difficult to predict insect performance under climate change from thermal performance curves alone (Andrew et al . ).…”

Section: Discussionmentioning

confidence: 97%

Experimental warming alters the relative survival and emigration of two dung beetle species from an Australian dung pat community

Holley

2019

Austral Ecology

Self Cite

To preserve insect-mediated ecosystem services under ongoing climate change, it is necessary to first understand the impact that warming will have on the insects that provide or mediate these services. Furthermore, because responses of a species may be modified by interactions with competitors, it is informative to examine warming effects on organisms and service provision under competition. Dung beetles provide numerous services to agriculture by burying the manure of other animals. To understand the potential impacts of climate warming on ecosystem service provision, we exposed two dung beetle species (Sisyphus rubrus and Euoniticellus fulvus (Coleoptera: Scarabaeidae)), occurring together in the same experimental pats, to warming and measured reproduction (dung ball production and burial, brood production, and egg laying), pat departure behaviour and survival of both species. These two species are likely competitors in pastures in northern New South Wales. To simulate climate warming, we used custom-built chambers to add offsets (+0, +2 or +4°C) to field recorded, diurnally fluctuating baseline temperatures. There was no direct effect of increased temperature on any measured trait in either species. We did find however that the relative survival of the two species depended on temperature; S. rubrus had a higher probability (resulting in greater odds) of surviving than E. fulvus in the +0 and +4°C offset chambers, but not in the +2°C offset chambers. Likewise, the relative likelihood of the different species leaving a dung pat was temperature dependent; in the +2°C offset chambers, E. fulvus were more likely to leave than S. rubrus, but not in the +0 and +4°C offsets chambers. Our results highlight that it may be important for future studies to consider warming effects on relative survival and emigration because such effects could potentially lead to changes in dung beetle species composition.

“…At the end of both experiments, the thermolimit respirometry ( Lighton and Turner, 2004 ; Andrew et al, 2016 ) was assessed in the fifth instar of caterpillars in the exposure of lowest concentration of Spinetoram and Azadirachtin as well as their control groups. Metabolic rate, activity and water loss were measured over a 25–55°C temperature range in a water bath (Type R4, Grant Instruments, Cambridge, United Kingdom).…”

Section: Methodsmentioning

confidence: 99%

Influence of Non-lethal Doses of Natural Insecticides Spinetoram and Azadirachtin on Helicoverpa punctigera (Native Budworm, Lepidoptera: Noctuidae) Under Laboratory Conditions

Betz

2020

Front. Physiol.

Self Cite

Helicoverpa punctigera (native budworm) is an important pest species in crops across Australia. From the third instar onward, this species causes severe damage to crop plants: therefore, caterpillars need to be managed at an early stage of their development. In our experiment, we raised H. punctigera on an artificial diet, which included different concentrations of the natural insecticides Spinetoram and Azadirachtin. The survival of the larvae, growth and body mass gain was recorded over 17 days. Only caterpillars raised on lowest toxin concentrations survived and molted successfully to the fifth instar, but had slower growth and body mass gain compared to the insecticide-free control group. Caterpillars fed on higher toxin concentrations never molted to the next instar or died in the first few days. To test how the toxins influence physiological conditions including metabolic rate and water loss, surviving fifth instar larvae were exposed to thermolimit respirometry: starting at 25°C following a constant increasing temperature ramping rate of 0.25°C –1 , until reaching the critical thermal maxima (CT max ). Caterpillars raised on a non-lethal dose of insecticides had higher metabolic rates and lost more water compared to the control group. Insects that have seem to consume more energy per mg tissue and have a higher water loss at high temperatures. Non-lethal concentrations of insecticides on pest insects physiology may reduce their impact on crops and may enable more targetted insecticide application.