Provenance assignment of insect samples with stable isotope markers

Reading natural abundance biogeochemical markers using mass spectrometry is a powerful tool for tracing ecological pathways as well as provenance determination of commercial products and items of forensic interest.  Although significant potential exists for such signals to elucidate the movement of insects – including high risk biosecurity pests – biogeochemical science in entomology remains poorly utilized.  This field in entomology is still in a phase of basic development, and many of the fundamental principles have until recently been minimally researched.

Here we will introduce and briefly review the limited literature that regards tracking insect movement using natural abundance biogeochemical markers.  Progress will be summarized through our own research where the internationally distributed pest, Helicoverpa armigera [Lepidoptera: Noctuidae], has been used to evaluate the potential for entomological provenance resolution through multiple climatically and geologically linked spatial markers (δ²H, ⁸⁷Sr/⁸⁶Sr, ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb isotope ratios and trace element concentration signatures) from single specimens.  In a comparison of moths from Australia and New Zealand, none of these markers were individually able to separate moths from different regions that were 150 – 3000km apart.  However, when used together in a multivariate analysis, the region of origin was correctly identified for approximately 75% of individual H. armigera samples.

This species, along with others of biosecurity interest, such as the brown marmorated stink bug (Halyomorpha halys, Pentatomidae), light brown apple moth (Epiphyas postvittana, Tortricidae) and Queensland fruit fly (Bactrocera tryoni, Tephritidae), have since been used to also examine processes fundamental to the location-to-plant-to-insect biogeochemical profile imprinting, including the turnover of elements in adult insect tissues, the influence of polyphagy and the effect of local variation in precipitation isotopic composition.  From this work, the potential and constraints of this technology are revealed, and future research needs proposed.