Determining the geographical origin of priority insect pest detections: anthropogenic stable isotope signatures to improve resolution of high risk environments

Specifically we will test if lead (Pb) isotopes, can improve the spatial resolution afforded by 87Sr/86Sr in urban and peri-urban areas.We propose to sample with reference to geological variation in and around Melbourne, Adelaide and Perth as examples of cities that are gateways to agriculturally productive areas for the grains, horticulture and wine industries.

Plant material will be sourced from 80 - 100 sites in each of these localities and analysed for Sr and Pb isotopes using the new mass spectrometry method developed at QUT[11, 13]. Plants offer a precise measure of locality compared to mobile insects and we have demonstrated prior with fruit flies that the isotopic signature for 87Sr/86Sr does not change between plant and fly, and there is no suggestion that this would be any different for the isotopes of lead[4].

A statistical comparison will be made of the resolution possible with the separate isotope systems and that for the Sr and Pb isotope systems combined.

A conclusion will be derived as to whether the addition of Pb is a useful strategy to improve assignment of an unknown specimen as of local (where it was found and likely established) or non-local (not established) origin.

At the very least, if Pb does not show improved predictive resolution of urban environments, gathering of 87Sr/86Sr data through this project will improve our knowledge of these areas, and subsequently our forensic capabilities, which is not anticipated to be supplied to this degree by aligned research.