Recombination between two amplified esterase alleles in Culex pipiens

Esterase gene amplification at the Ester superlocus provides organophosphat e resistance in the mosquito Culex pipiens (L.). In this study we explored the possibility of recombination between two amplified esterase alleles, th us generating a composite amplified allele. To do that, females heterozygou s for two distinct amplified alleles (Ester(2) and Ester(4)) were crossed w ith males homozygous for a third resistance allele (Estet(8)). Among analyz ed offspring, one recombinant composite allele (Ester(2-4)) was detected, p roviding a rate of recombination of approximately 0.2%. This is the first r eport of a recombination between two distinct amplified esterase alleles, T his phenomenon renders the predictability of allele evolution considerably more complex than was previously thought.