Tracking Global Invasion Pathways of the Spongy Moth (Lepidoptera: Erebidae) to the U.S. using Stable Isotopes as Endogenous Biomarkers

The spread of invasive insect species causes enormous ecological damage and economic losses worldwide. A reliable method that tracks back an invaded insect’s origin would be of great use to entomologists, phytopathologists and pest managers. The spongy moth (Lymantria dispar (L.d.), Linnaeus 1758) is a persistent invasive pest in the north-eastern United States (U.S.) and periodically causes major defoliations in temperate forests. We analysed field-captured (Europe, Asia, U.S.) and lab-reared L.d. specimens for their natal isotopic hydrogen and nitrogen signatures imprinted in their biological tissues (δ2H and δ15N) and compared these values to the long-term mean δ2H of regional precipitation (Global Network of Isotopes in Precipitation) and δ15N of regional plants at the capture site. We established the percentage of hydrogen-deuterium exchange for L.d. tissue (Pex=8.2%) using the comparative equilibration method and two-source-mixing-models, which allowed the extraction of the moth’s...