COMMENSALISM, ADAPTATION AND GENE FLOW - MOSQUITOS OF THE CULEX-PIPIENS COMPLEX IN DIFFERENT HABITATS

Two ecotypes have been described for Culex pipiens mosquitoes of the t emperate zone: a human commensal type and a feral type, but their degr ee of evolutionary differentiation and taxonomic status are still uncl ear. The commensal form is characterized by life-history traits probab ly adaptive to underground man-made environments. This situation has s ometimes been considered as an example of recent speciation although t he existence of intermediate forms indicates that the balance between gene flow and disruptive selection should first be assessed. The prese nt study was concerned with (1) the determination of biological traits involved in adaptation to commensalism, and (2) the pattern of gene f low within and between ecotypes in a restricted area, It was found tha t (1) significant differences in biological traits exist between mosqu itoes from different habitats, (2) characteristics of the commensal ty pe are not universal in mosquitoes from underground manmade habitats, (3) allozyme markers do not clearly differentiate ecotypes and (4) ins ecticide resistance genes, which reveal recent migration, occur in eac h ecotype. These results are discussed in the context of possible spec iation due to commensalism.