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L M Cook

Publications and source records attributed to L M Cook.

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Phenotypic variability and heterozygosity at an esterase locus in the mosquito Aedes aegypti.

Populations of the yellow fever mosquito, Aedes aegypti L. are polymorphic for esterase alleles. This could be because the alleles are neutral or because selection protects the polymorphism, as had been concluded from a study of allele frequencies. A test has been carried out to look for possible associations of esterase heterozygosity with speed of development, body size and spine number symmetry in two spine rows. Heterozygotes were found to be larger and slower growing than homozygotes, but there was no difference in degree of asymmetry. There were fewer heterozygotes and a greater deficiency compared with expectation in insects reared at higher temperatures. It is concluded that different genotypes do differ in fitness.

Aedes

What can be learnt about selection from gene frequency distribution?

Polymorphism has been studied at the Esterase 6 locus in the Yellow Fever mosquito Aedes aegypti (L.) in laboratory stocks. At least 12 alleles are present, with up to four coexisting in a stock. The allele frequency distribution is quite sharply peaked at a mode of about 0.25. The experimental data are compared with the results of simulation based on two models, one in which the initial global distribution is taken to be the stationary distribution obtained from the neutral model assuming M = 4 mu Ne = 1 and the other in which the initial global distribution is generated from the experimental populations studied. The results suggest that the patterns observed are not likely to arise through random fluctuation of frequencies in neutral alleles, but that some kind of selection maintains polymorphism, either in the wild or in the laboratory, or both.

Aedes