Anàlisi sobre dos ecotipus de Culex (Culex) pipiens Linnaeus, 1758 (Diptera: Culicidae) al Baix Llobregat

Abstract

Taxonomic differentation was assessed in the mosquito species-complex Culex pipiens Linnaeus, 1758. The working hypothesis was that autogenous populations (i.e. those containing females that can lay their first egg batch without a blood meal) could represent a separate species, Culex molestus, morphological differentiated and ecologically isolated in closed underground habitats. A total of 74 populations were sampled from different habitats in the Baix Llobregat area, near Barcelona in Spain, during 1993 and 1994 in order to assess autogeny, morphology, population dynamics and gene flow between habitats. Larval populations from closed underground habitats showes a higher percentage of auto- genous females. The autogeny was related to certain morphological characters, although these lacked diagnostic value. Since the gene flow between habitats was estimated to be high, the taxonomic validity of Culex molestus is not supported, and the autogeny is considered to be only a physiological adaptation. In addition, analysis of organophosphate pesticide resistance revealed high frequencies of resistance alleles up to two years after the withdrawal of these products. Maintenance of the resistance could be favoured by agricultural pesticide residues in the water. A dynamic model is proposed that incorporates this data and also includes the influence of human mosquito-control activities as a factor increasing genetic drift.