GENE FLOW AMONG TETRANYCHUS-URTICAE (ACARI, TETRANYCHIDAE) POPULATIONS IN GREECE

Polymorphism of four enzymatic loci has been examined in 27 population s of Tetranychus urticae in relation to their geographical distributio n and to two ecological parameters: open field vs. greenhouse habitats , and species of the colonized host plant. Genetic differentiation was significantly correlated to geographical distance in both types of ha bitat. Mite density and distribution of infested plants appear to be i mportant factors for the population structure of T. urticae. In open f ield, T. urticae specimens from citrus trees were genetically more sim ilar to other 'citrus' samples collected in different localities than they were from mites collected in the same locality on other plant spe cies.