Molecular data reveal a cryptic species within the Culex pipiens mosquito complex

The Culex pipiens mosquito complex is a group of evolutionarily closely related species including the common house mosquito, Cx. pipiens, and the southern house mosquito, Cx. quinquefasciatus, which both are infected by the cytoplasmically inherited Wolbachia symbiont. A Wolbachia-uninfected population of Cx. pipiens was however described in South Africa and was recently proposed to represent a cryptic species where Wolbachia spread has been prevented by reproductive isolation. In this study, we reconsider the existence of this novel species by undertaking an extensive screening for the presence of Wolbachia-uninfected Cx. pipiens specimens and by characterizing their genetic relatedness with known members of the complex. We first reported on the presence of Wolbachia-uninfected specimens in several Cx. pipiens breeding sites in Europe and North Africa. Using a multi-locus typing scheme, we next confirm that these uninfected specimens unambiguously belong to the Cx. pipiens complex. While, uninfected specimens shared ancestral nuclear DNA polymorphism with infected Cx. pipiens specimens, they also harbor novel mitochondrial haplotypes which are closely related, but different, to those found in all other Cx. pipiens complex members. Overall, these results corroborate the presence of a cryptic species within the Cx. pipiens complex where ancestral levels of mitochondrial diversity have been maintained. We further evidence a geographic distribution far wider than previously suspected, ranging from the North of Europe to the South of Africa.