Comparative performance of a multi-locus barcoding approach to enhance taxonomic resolution of New Zealand mosquitoes (Diptera: Culicidae)

Abstract

Mosquitoes (Diptera: Culicidae) pose a serious threat to human health globally and the accurate identification of mosquito species is fundamental to entomological diagnostics and surveillance implementing effective vector control and management. However, cryptic species complexes, incomplete or damaged specimens, and juvenile life stages complicates the task. Molecular characterisation has shown the potential to identify the mosquito species accurately and overcomes the difficulties that morphological diagnosis face. Here, we assessed the effectiveness of a multi-locus barcoding approach using cytochrome c oxidase subunit I (COI), internal transcribed spacer 1 (ITS1) and internal transcribed spacer 2 (ITS2) regions to identify the New Zealand mosquito species (n = 16) at the highest taxonomic resolution, which can make diagnosis more accurate and efficient. Our results show that most of the New Zealand mosquito species could be distinctly separated from each other as well as from other exotic species using either of these barcoding regions (i.e., COI, ITS1 and ITS2). The assessment of taxonomic discriminatory power of COI, ITS1 and ITS2 barcodes suggests that ITS2 can better distinguish the New Zealand closely-related species. Two closely-related endemic species from the Culex pervigilans species complex (Cx. rotoruae and Cx. pervigilans) were difficult to distinguish using COI and ITS1 regions. However, the ITS2 barcode could detect a greater genetic variation among individuals of those two species and demonstrate the potential to resolve the relationships among them to provide better resolution as a complementary to COI. Overall, this study provides a reference DNA barcode database of COI and ITS2 for New Zealand mosquito species, which will aid in their accurate identification at a higher taxonomic resolution and corroborate the traditional morphological approaches to perform better species discrimination among closely-related species complex. The study also assessed the preliminary genetic diversity of the mosquito species from different regions of New Zealand, which can be used as a baseline for uncovering the environmental and geographical effect on genomic variations among New Zealand mosquito populations in the future.