Population structure in the spider mite Tetranychus urticae (Acari: Tetranychidae) from Crete based on multiple allozymes.

The polymorphism of four isozymes was studied on single females of Tetranychus urticae from Crete (Greece), using an isoelectric focusing technique. Genetic differentiation was found to be correlated with distance but not with the species of colonized host-plants. Thus no differentiation was observed between samples collected on citrus trees, tomato, pumpkin, okra or weed plants located within a 50 m(2) area, showing that at this geographical scale T. urticae populations are panmictic. In contrast, samples from plants at 150 m or more from one another displayed a significant genetic differentiation. These results are discussed in relation to the known pattern of migration in the species.