Molecular resources for the stored grain Cryptolestes cryptic pest species (Coleoptera: Laemophloeidae)

Abstract

Recent research activities relating to evolutionary genetics and molecular characterisation of the stored grain Cryptolestes (Ganglbauer) beetle pest species have revealed gaps in public DNA databases, and resulted in molecular diagnostic inconsistencies. This study reports on characterisation of the mitochondrial DNA cytochrome oxidase I (mtCOI) gene from specimens detected during biosecurity inspections at Australias border, and surveys of publicly available mtCOI gene sequences, for re-assessment of Cryptolestes species status. The results enabled clarification of a new putative C. sp. WTT-2016 species, and supported the close evolutionary relationships between C. ferrugineus (Stephens)/C. pusilloides (Steel and Howe), and between C. pusillus (Schonherr) and the previously identified C. sp. WTT-2013 cryptic species. Widespread confusion between C. ferrugineus, C. pusiolloides, C. pusillus and the two putative novel C. sp. WTT-2013 and C. sp. WTT-2016, highlighted the taxonomic challenge surrounding this beetle genus, while inter-specific genetic distances between C. spartii (Curtis)/C. corticinus (Reitter) suggested they belonged to the same species. Assembled and annotated mitochondrial DNA genomes (mitogenomes) of six Cryptolestes species via high throughput sequencing identified assembly errors associated with published mitogenomes of C. ferrugineus and C. turcicus (Grouvelle), and misidentification of C. pusillus. Based on re-evaluation of intra- and inter-specific genetic distances and congruence from phylogenetic inferences, we proposed a Cryptolestes species genetic gap at approximately 5% that could help with defining species boundaries. By reconciling these molecular incongruences, this study will contribute to improving agricultural biosecurity preparedness associated with the economically important Cryptolestes flat grain beetle species.