Laboratory experiments on a change in genetic structure with an increase of population density in the citrus red mite population, Panonychus citri (McGregor) (Acari : Tetranychidae)

Abstract

A change in genetic structure with an increase of population density in Panonychus citri was analyzed by laboratory experiments focusing on the inbreeding coefficient (F) and spatial distribution. Genotype frequencies of an esterase locus, a-Estl, in F₁ females after mating in various population densities suggested that P. citri mated randomly. Adult females introduced to small citrus seedlings laid most eggs on the leaves on which they were set. The majority of immature offspring stayed on the leaves where they hatched. Females with different homo genotypes were introduced on leaves at the top and bottom of seedlings separately. The inbreeding coefficients of the developing populations were kept high for at least a month. A Iinear relationship was observed between mean density of adult females and F. From these results, we concluded that the aggregated egg production by adult females and low dispersion rate in the immature stages strongly restricts hybridization among breeding Patches of this secies.