a1 Laboratoire Génétique et Environment, Institut des Sciences de l'Evolution (CNRS URA 327), Case Courrier 065, Université Montpellier II, Place Eugène Bataillon, 34095 Montpellier cedex 05, France
a2 Servei de control de mosquits, Consell comarcal del baix Llobregat, Parc Torreblanca, Ctra N 340, 08980 Sant Feliu de Llobregat, Spain
a3 Department of Genetics, Uppsala university, Box 7003, S-75007 Uppsala, Sweden
Two ecotypes have been described for Culex pipiens mosquitoes of the temperate zone: a human commensal type and a feral type, but their degree of evolutionary differentiation and taxonomic status are still unclear. The commensal form is characterized by life-history traits probably adaptive to underground man-made environments. This situation has sometimes been considered as an example of recent speciation although the existence of intermediate forms indicates that the balance between gene flow and disruptive selection should first be assessed. The present study was concerned with (1) the determination of biological traits involved in adaptation to commensalism, and (2) the pattern of gene flow within and between ecotypes in a restricted area. It was found that (1) significant differences in biological traits exist between mosquitoes from different habitats, (2) characteristics of the commensal type are not universal in mosquitoes from underground man-made habitats, (3) allozyme markers do not clearly differentiate ecotypes and (4) insecticide resistance genes, which reveal recent migration, occur in each ecotype. These results are discussed in the context of possible speciation due to commensalism.
(Received January 27 1995)
(Revised May 15 1995)
c1 Author for correspondence.