Compatibility between strains ofTetranychus pueraricola(Acari: Tetranychidae) Correlated with distance between sites of their origin

To test the hypothesis that the degree of incompatibility between strains of mites is correlated with the distance between the areas of their origin, seven local strains of Tetranychus pueraricola Ehara and Gotoh (Acari: Tetranychidae) were crossed with the Hitachi-ohta (Ho) and the Onoma (On) strains. For each F1 generation obtained from crosses between the On strain and local strains, the number of eggs laid per female, egg hatchability, survival rate in immature stages, female ratio and average number of female offspring produced per female were similar to the values obtained in crosses of the On parent strain. Similar results were obtained for crosses between the Ho strain and all but one of the local strains. However, egg hatchability and average number of female offspring produced per female in the B1 generation were less than those in the F1 generation with large variations among cross combinations. The female ratio was significantly higher in the B1 generation than in the F1 generation. Thus, the F1 generations obtained from crossings between any two strains were viable and fertile, but the degree of incompatibility in the B1 generation varied from almost infertile to fertile. If compatibility in any one cross combination is estimated by “egg hatchability” and “female ratio”, the compatibility in the B1 generation was significantly correlated with the distance between the areas of their origin.