DNA analysis of invasive ant guts to determine predation of Episimus utilis in Hawaii

Episimus utilis (Lepidoptera: Tortricidae) caterpillars were released in Hawaiʻi as a biocontrol agent against Brazilian peppertree (Schinus terebinthifolia) in 1954. Contrary to expectations, these caterpillars have had little impact on the spread and abundance of S. terebinthifolia in Hawaiʻi. The primary objective of our study is to determine if ant predation is playing a role in limiting the success of E. utilis against Brazilian peppertree. Ant samples were collected from various locations on Oʻahu with an abundance of Brazilian peppertree and E. utilis. After collection, the contents of the ants’ guts were analyzed. DNA extraction was performed using a Qiagen blood and tissue kit, and samples were sent for illumina sequencing using cytochrome oxidase I (COI) to determine if E. utilis DNA could be found among the prey species present in the ants' guts.The ant species examined include: Pseudomyrmex gracilis (Hymenoptera: Pseudomyrmecinae), Linepithema humile (Dolichoderinae), Plagiolepis alluaudi (Formicinae), Ochetellus glaber (Dolichoderinae), Brachymyrmex obscurior (Formicinae), and Anoplolepis gracilipes (Formicinae). Results from this study will help determine if ant predation is an important factor in limiting the success of E. utilis in controlling Brazilian peppertree populations. This will help guide future introductions of biocontrol for the Brazilian peppertree in Hawaiʻi and weed biocontrol in general.