Hidden in plain sight: phylogeography of an overlooked parasitoid species Trioxys sunnysidensis Fulbright & Pike (Hymenoptera: Braconidae: Aphidiinae)

The bird cherry-oat aphid Rhopalosiphum padi is a major cereal pest with an almost cosmopolitan distribution. As one of the main groups of biocontrol agents for aphids, numerous Aphidiinae are associated with R. padi, including the genera Binodoxys and Trioxys. As a recently described species parasitizing R. padi, Trioxys sunnysidensis is recorded from Europe for the first time based on morphological and molecular data. Specimens from North America, Europe and New Zealand were used in the analysis of the cytochrome c oxidase subunit I to explore genetic variation among populations. The analysis revealed one of the highest haplotype diversities in Aphidiinae so far, with 25 haplotypes detected. The two most common haplotypes are shared across groups of populations, whereas all of the others are found either in North America or Europe. Because the genetic structure of populations is an important factor to consider when choosing a biocontrol agent, the results obtained in the present study may be helpful in guiding potential biocontrol attempts.