Comparative analysis of mitochondrial genomes of geographic variants of the gypsy moth, Lymantria dispar, reveals a previously undescribed genotypic entity

Authors: DJOUMAD, ABDELMADJID - Canadian Forest Service; NISOLE, AUDREY - Canadian Forest Service; ZAHIRI, REZA - Canadian Food Inspection Agency; FRESCHI, LUCA - Laval University; PICQ, SANDRINE - Canadian Forest Service; Gundersen-Rindal, Dawn; Sparks, Michael; DEWAR, KEN - McGill University - Canada; STEWART, DON - Canadian Forest Service; MAAROUFI, HALIM - Laval University; LEVESQUE, ROGER - Canadian Forest Service; HAMELIN, RICHARD - Canadian Forest Service; CUSSON, MICHEL - Canadian Forest Service

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2017
Publication Date: 10/27/2017
Citation: Djoumad, A., Nisole, A., Zahiri, R., Freschi, L., Picq, S., Gundersen, D.E., Sparks, M., Dewar, K., Stewart, D., Maaroufi, H., Levesque, R.C., Hamelin, R.C., Cusson, M. 2017. Comparative analysis of mitochondrial genomes of geographic variants of the gypsy moth, Lymantria dispar, reveals a previously undescribed genotypic entity. Scientific Reports. https://doi.org/10.1038/s41598-017-14530-6.
DOI: https://doi.org/10.1038/s41598-017-14530-6

Interpretive Summary: The gypsy moth is a remarkably destructive forest pest occurring in numerous parts of the world, including the North American continent. The gypsy moth subspecies ordinarily observed in North America is the European gypsy moth (Lymantria dispar dispar), whose females are flightless. Two Asian subspecies, L. dispar asiatica and L. dispar japonica, have flight-capable females, which highly elevates their potential for causing forest damage relative to the European variant. As such, the development of more sensitive and specific molecular diagnostics with which to detect these more destructive Asian variants is very important for defending natural resources in the United States and Canada. Previous molecular diagnostic tools include those targeting the so-called mitochondrial barcode region. In this study, the complete mitochondrial genomes (mitogenomes) of 10 geographic variants of L. dispar were sequenced and analyzed, resulting in the identification of new regions of variability with which to target using diagnostic tools. These results will help in developing new molecular tools with greater utility than those currently available. In addition, this study determined that a gypsy moth population present in northern Iran—with potential for introduction to North America via trade routes passing through the Black Sea—has a mitogenome quite distinctive from those of the European and Asian L. dispar subspecies populations sampled. As such, this “Caucasian” gypsy moth population may potentially represent a novel species, phylogenetically intermediate to L. dispar and the so-called Hokkaido gypsy moth species, Lymantria umbrosa. This information will be used by scientists, companies, and regualotry agencies interested in control of the gypsy moth.

Technical Abstract: The gypsy moth, Lymantria dispar L., is one of the most destructive forest pests in the world. While the subspecies established in North America is the European gypsy moth (L. dispar dispar), whose females are flightless, the two Asian subspecies, L. dispar asiatica and L. dispar japonica, have flight-capable females, enhancing their invasiveness and warranting precautionary measures to prevent their permanent establishment in North America. Various molecular tools have been developed to help distinguish European from Asian subspecies, several of which are based on the mitochondrial barcode region. In an effort to identify additional informative markers, we undertook the sequencing and analysis of the mitogenomes of 10 geographic variants of L. dispar, including two or more variants of each subspecies, plus the closely related L. umbrosa as outgroup. Several regions of the gypsy moth mitogenomes displayed nucleotide substitutions with potential usefulness for the identification of subspecies and/or geographic origins. Interestingly, the mitogenome of one geographic variant displayed significant divergence relative to the remaining variants, raising questions about its taxonomic status. Phylogenetic analyses placed this population from northern Iran as basal to the L. dispar clades. The present findings will help improve diagnostic tests aimed at limiting the risks of Asian gypsy moth invasions.