• Energy Research

Mitigate+: Research for Low-Emission Food Systems

The relative thermal requirements and tolerances of hymenopteran parasitoids and their hosts were investigated based on published data. The optimal temperature (Topt) for development of parasitoids was significantly lower than that for their hosts. Given the limited plasticity of insect responses to high temperatures and the proximity of Topt to critical thermal maxima, this suggests that host-parasitoid interactions could be negatively affected by increasing global temperatures. A modelling study of the interactions between the diamondback moth and its parasitoid Diadegma semiclausum in Australia indicated that predicted temperature increases will have a greater negative impact on the distribution of the parasitoid than on its host and that they could lead to its exclusion from some agricultural regions where it is currently important.

The southern paralysis tick, Ixodes cornuatus, is a tick of veterinary and medical importance in Australia. We use two methods, CLIMEX, and an envelope-model approach which we name the 'climatic-range method' to study the climatic requirements of I. cornuatus and thus to attempt to account for the geographic distribution of I. cornuatus. CLIMEX and our climatic-range method allowed us to account for 94% and 97% of the records of I. cornuatus respectively. We also studied the host preferences of I. cornuatus which we subsequently used in conjunction with our species distribution methods to account for the presence and the absences of I. cornuatus across Australia. Our findings indicate that the actual geographic distribution of I. cornuatus is smaller than the potential geographic range of this tick, and thus, that there are regions in Australia which may be suitable for I. cornuatus where this tick has not been recorded. Although our findings indicate that I. cornuatus might be able to persist in these currently unoccupied regions, our findings also indicate that the potential geographic range of I. cornuatus may shrink by 51 to 76% by 2090, depending on which climate change scenario comes to pass.