Abstract
Ecotypic differentiation is well described in the mosquito Culex pipiens , separating populations breeding in subterranean and human‐made sites (hypogeous habitat) from those in open‐air sites (epigeous habitat). The pattern of population differentiation observed at the Aat‐1 locus has been suspected to be associated with such ecotypic differentiation via habitat‐dependent selection, but this supposition is still the subject of debate in the literature. We analysed differentiation patterns for Aat‐1 and another four loci among populations from both habitat types in the French Alps. We showed that the Aat‐1 A allele is favoured within hypogeous habitats but selected against within epigeous habitats. Comparisons of our results with other data reported in the literature indicate that the Aat‐1 A allele is generally evolving under habitat‐differential selection, but that the precise balance of migration and selection that determines equilibrium allele frequencies varies greatly across Europe. The nature of this habitat‐dependent selection, and its resulting (geographically varying) equilibrium point, are discussed in relation to the biology of this mosquito species.