DNA Barcoding of west European Strachiini questions the validity of several species of the genus Eurydema (Hemiptera. Heteroptera: Pentatomidae)

The pentatomid tribe Strachiini includes numerous crop pests, notably the genus Eurydema Laporte, 1833, which comprises Palaearctic species feeding on cruciferous plants. In a context of reduced pesticide use and increased biological invasions, the damage caused by Strachiini to European crops has increased over the past few years. Rapid identification of these pests at all stages of their development is therefore becoming crucial.

In this context, we investigated whether DNA barcoding can reliably distinguish all developmental stages of Western European Strachiini species and invasive congeners. We analysed 325 specimens collected worldwide, using both newly generated in-home and publicly available COI sequences. Species boundaries were assessed through distance-based and phylogenetic tree-based methods, including Neighbor-Joining (NJ) and Maximum Likelihood (ML).

Morphological identification of Strachiini was generally consistent and reached a consensus, except for a few challenging species pairs such as Eurydema fieberi Schummel, 1837 / E. rotundicollis (Dohrn, 1860) and Eurydema s pectabilis Horváth, 1882 / E. eckerleini Josifov, 1961. We therefore used as reference material in this study, specimens preserved in institutional or private collections, consensually identified by several generations of specialists.

Our results confirms that Eurydema species of agronomic importance and their related invasive congeners can be reliably identified through DNA barcoding except for several species within the large genus Eurydema, for which discrepancies between morphological and molecular identifications were highlighted. A curated set of validated sequences has been deposited in the BOLD Systems (id.boldsystems.org/), GenBank, NCBI (https:// www.ncbi.nlm.nih.gov/) and ARTHEMIS databases (arthemisdb.supagro.inrae.fr/) to support accurate molecular identification.

The taxonomic issues highlighted in the large genus Eurydema are discussed. They will require further investigation and may lead to necessary taxonomic revisions, hence, some of these (e.g. involving the widespread pest species E. ornata) could have agronomic implications.