Abstract
The polymorphism of 4 enzymatic systems of 21 Tetranychus urticae samples collected in southern France was analyzed in order to ascertain genetic differentiation within and between greenhouses. Genetic structure was investigated in relation to mite density, geographic distribution of greenhouses and the colonized host plant. We found that mite density and distribution of infested plants influence gene flow within greenhouses. Between greenhouses isolation by distance was significant. Differentiation did not appear to be associated with the colonized plant species.