Unravelling Mosquito Species Complex Through DNA Barcodes: Complementing Morphological Identification for Accurate Discrimination

Abstract

Mosquitoes are the most recognizable insects distributed throughout the globe including tropical and sub-tropical zones. Accurate and precise mosquito species identification is crucial in many prospects including developing species-specific vector control strategies. Mosquito vectors transmit various disease causative pathogens, our studies about them not merely desire to a complete taxonomic survey of their bio-fauna but also their consequences on human public health. Except for a few siblings or closely related species, mosquito taxonomy based on Linnaean classification has stagnated for more than a century at the stage of recognizing and naming different species. The Linnaean classification of mosquito species is certainly limited since it does not consider phenotypic plasticity, genetic variation of individuals including the morphological complexity, e.g. the occurrence of cryptic taxa or keys only developed for a certain gender or life stages. In recent times, the lack of experienced taxonomists demands the shifting of identification methods from Linnaeus to DNA-based approach such as DNA barcodes which are considered as a moot point in identifying mosquito vectors at their any life stages. At present, the genomic as well as mitochondrial genes are extensively utilized in the phylogenetic analysis of mosquito species. Moreover, the utility of a single even a partial mitochondrial DNA (mtDNA) sequence such as cytochrome oxidase I (COI/COX1) gene can be considered as the initial point for categorizing mosquito biodiversity. The mitochondrial genome appears to be highly suited for barcoding as it lacks introns and its maternal inheritance property is also beneficial for barcoding studies. Additionally, due to more conserved regions within species, the COI gene creates strong phylogenetic signals for accurate species identification. Often more than one marker such as mitochondrial along with nuclear genes is also used for species discrimination. However, DNA barcoding is not an end but it will boost the rate of species identification and it also solves the morphological ambiguity arises within species complex and also helps in discriminating the exotic species from endemic mosquito species. The unique contribution of DNA barcoding to mosquito taxonomy and systematics is a compressed timeline for the exploration of its diversity. Moreover, the molecular data are also widely used for producing molecular phylogenies such as phylogenetic, phylogeographic, population genetics and species identification studies. Phylogeography and genetic variation within the species provide knowledge about the origin and migration of the species which further contribute to vector surveillance and vector control strategy. Phylogenetic trees are also utilized to analyse gene duplication, estimating rates of diversification, polymorphism, recombination, population dynamics and inferring organismal phylogenies by combining it with other data sources. This chapter confers about problems associated with mosquito species complex and the implementation of DNA barcoding in their identification as well as the management process.