Genetical Research



Insecticide resistance genes induce a mating competition cost in Culex pipiens mosquitoes


CLAIRE  BERTICAT  a1 c1, GRÉGOIRE  BOQUIEN  a1, MICHEL  RAYMOND  a1 and CHRISTINE  CHEVILLON  a1
a1 Genetics of Adaptation, Laboratoire Génétique et Environnement, Institut des Sciences de l'Evolution (UMR CNRS 5554), Université de Montpellier II (C.C. 065), F-34095 Montpellier cedex 05, France

Abstract

Resistance to organophosphorus insecticides (OP) in Culex pipiens mosquitoes represents a convenient model for investigating the fitness cost of resistance genes and its origin, since both the environmental changes in nature and the adaptive genes are clearly identified. Two loci are involved in this resistance – the super-locus Ester and the locus Ace.1 – each displaying several resistance alleles. Population surveys have shown differences in fitness cost between these resistance genes and even between resistance alleles of the same locus. In order to better understand this fitness cost and its variability, the effects of these resistance genes on several fitness-related traits are being studied. Here, through competition experiments between two males for the access to one female, we analysed the effect on paternity success associated with three resistance alleles – Ester4, Ester1 and Ace.1R – relative to susceptible males and relative to one another. The eventual effect of female genotype on male mating success was also studied by using susceptible and resistant females. The strains used in this experiment had the same genetic background. Susceptible males had a mating advantage when competing with any of the resistant males, suggesting a substantial cost of resistance genes to this trait. When competing against susceptible males, the paternity success did not vary among resistant males, whatever the genotype of the female. When competing against other resistant males, no difference in paternity success was apparent, except when the female was Ester1.

(Received May 23 2001)
(Revised September 14 2001)


Correspondence:
c1 Corresponding author: Fax: +33 4 67 14 36 22. e-mail: berticat@isem.univ-montp2.fr


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