DIRECT AND INDIRECT SELECTION ON BEHAVIORAL-RESPONSE TO PERMETHRIN IN LARVAL DIAMONDBACK MOTHS (LEPIDOPTERA, PLUTELLIDAE)

Both physiological tolerance to the pyrethroid permethrin and behavioral response to permethrin have been shown to have some genetic basis in the diamondback moth, Plutella xylostella (L.). Hence, selection based on these characters should be possible. We investigated the direct and indirect effects of selection on physiological tolerance and behavioral responsiveness, and how these effects vary across populations. Working with four populations for which genetic information was available, we created three groups within each population by selecting for behavioral responsiveness and unresponsiveness, and by separately selecting for physiological tolerance. Tile effects of selection were evaluated by assaying the offspring of these groups. In all four populations, the dominant effects of selection were on physiological tolerance. Physiological tolerance was higher in those groups selected directly based on tolerance, and those selected for behavioral unresponsiveness, than in the groups selected for behavioral responsiveness. In addition, tolerance was higher in the groups selected for tolerance and behavioral unresponsiveness than in the parental generation in all but one population. We observed no clear patterns with respect to the behavioral character. Direct selection for responsiveness was successful in only one population. Selection based on tolerance did not indirectly produce shifts. in behavior. At least two elements of behavior, however were affected by selection: first, general responsiveness as shown by behavioral variation independent of permethrin; second, an increased tendency to avoid permethrin especially at high toxin concentrations. These effects varied among the populations apparently as a result of variation in genetic parameters.