GENETIC-STRUCTURE OF HALOTYDEUS DESTRUCTOR AND PENTHALEUS MAJOR POPULATIONS IN VICTORIA (ACARI, PENTHALEIDAE)

The redlegged earth mite (Halotydeus destructor) and the blue oat mite (Penthaleus major) are major pests of pastures and crops in southern Australia. Reproductive modes, migration rates and levels of different iation between populations were investigated using allozyme electropho resis. Collections were made throughout Victoria and a sample was also obtained from Western Australia. Three enzyme loci were polymorphic i n H destructor (Mdh-1, Mdh-2 and Idh). Genotype frequencies of these l oci did not differ between phenotypic males and females, providing no evidence for haplodiploidy. Allele frequencies were in Hardy-Weinberg equilibrium, indicating that H. destructor is diploid and sexual. This was confirmed via crosses between males and females. Allele frequenci es differed between Victorian sites, although F statistics indicated l ittle differentiation over all loci. A sample from Western Australia d id not differ in allele frequencies from the Victorian sites. Four pol ymorphic loci were found in P. major (Mdh-1, Mdh-2, Idh and Gpi). Only a few multilocus genotypes occurred in a sample, indicating that P. m ajor is parthenogenic. No male P. major were found in this study. A nu mber of colour morphs were also identified and a genetic association b etween genital plate colour and clonal type was found in one populatio n of P. major. Two different body colour morphs were associated with d ifferent clonal types.