Abstract
Understanding the population structure and mechanisms of taxa diversification is important for organisms responsible for the transmission of human diseases. Two vectors of West Nile virus, Culex pipiens pipiens and Cx. p. molestus, exhibit epidemiologically important behavioral and physiological differences, but the whole-genome divergence between them was unexplored. The goal of this study is to better understand the level of genomic differentiation and population structures of Cx. p. pipiens and Cx. p. molestus from different continents. We sequenced and compared the whole genomes of 40 individual mosquitoes from two locations in Eurasia and two in North America. Principal Component, ADMIXTURE, and neighbor joining analyses of the nuclear genomes identified two major intercontinental, monophyletic clusters of Cx. p. pipiens and Cx. p. molestus. The level of genomic differentiation between the subspecies was uniform along chromosomes. The ADMIXTURE analysis determined signatures of admixture in Cx. p. pipens populations but not in Cx. p. molestus populations. Comparison of mitochondrial genomes among the specimens showed a paraphyletic origin of the major haplogroups between the subspecies but a monophyletic structure between the continents. Thus, our study identified that Cx. p. molestus and Cx. p. pipiens represent different evolutionary units with monophyletic origin that have undergone incipient ecological speciation.
Highlights
Understanding the population structure and mechanisms of taxa diversification is important for organisms responsible for the transmission of human diseases
Similar results regarding the monophyletic origin of Cx. p. pipiens and Cx. p. molestus were obtained by the analysis of single nucleotide polymorphisms (SNPs) in the mitochondrial Cytochrome Oxidase I (COI) gene of European populations[23]
These conclusions were strongly supported by another work using amplified fragment length polymorphism markers that identified discrete genomic differences between the subspecies and, considered Cx. p. pipiens and Cx. p. molestus to be distinct evolutionary entities that are likely in the process of incipient speciation[24]
Summary
Understanding the population structure and mechanisms of taxa diversification is important for organisms responsible for the transmission of human diseases. Pipiens represent different evolutionary units with monophyletic origin that have undergone incipient ecological speciation. Distribution of Cx. australicus and Cx. globocoxitus is restricted to Australia In addition to these species, the Cx. pipiens complex includes a subspecies, Cx. p. Molestus from different continents cluster together in a subspecies specific manner and more likely represent two separate taxonomic units or species with a unique evolutionary history[19]. Molestus were obtained by the analysis of single nucleotide polymorphisms (SNPs) in the mitochondrial Cytochrome Oxidase I (COI) gene of European populations[23] These conclusions were strongly supported by another work using amplified fragment length polymorphism markers that identified discrete genomic differences between the subspecies and, considered Cx. p. We follow the classical nomenclature that was proposed by Mattingly in 1951 and consider Cx. p. pipiens and Cx. p. molestus as subspecies[21,22]
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