Revisiting the Evolutionary History of Culex molestus and Culex pipiens: Insights Beyond WWII Origin Narratives

Abstract

Culex is a genus of mosquitoes belonging to the family Culicidae. These species are the primary vectors for diseases like the West Nile virus, St. Louis encephalitis, lymphatic filariasis, and agricultural pests. The species are distributed all over the world with overlapping species distribution. To date, it is assumed that the Culex molestus ecotype originated and evolved in London underground tunnels during WWII, when people took shelter. We tested this hypothesis by constructing phylogenetic trees containing different ecotypes and species of Culex. We charted the ecological range of C.pipiens and C.molestus and investigated the evolutionary history of the Culex species using the CO1, IGS & ITS2 gene sequences. We find some indication that C.pipiens and C.molestus form a species complex at best. In all the phylogenetic trees we constructed, C.pipiens and C.molestus shared the same ancestor and showed long branch lengths indicative of a long evolutionary history. This indicates that C.molestus could not have evolved in London tunnels during WWII. C.pipiens in all the trees showed longer branch lengths as compared to C.molestus. Our study supports the concept that evolution selects from an already existing pool of genetic variants to evolve different ecotypes and species.