Variations in life history traits and flight capacity among populations ofthe light brown apple moth Epiphyas postvittana (Walker) (Lepidoptera : Tortricidae)

The empirical study of interpopulation variation in life history and other fitness traits has been an important approach to understanding the ecology and evolution of organisms and gaining insight into possible sources of var iation. We report a quantitative analysis for variations of five life histo ry traits (larval developmental time, adult body weight, adult lifespan, ag e at first reproduction, total fecundity) and flight capacity among populat ions of Epiphyas postvittana originating from four localities in Australia and one in New Zealand. These populations were compared at two temperatures (15 degrees and 25 degreesC) after being maintained under uniform laborato ry conditions for 1.5 generations, so that the relative role of genetic div ergence and phenotypic plasticity in determining interpopulation variation could be disentangled. Genetic differentiation between populations was show n in all measured traits, with the greatest divergence occurring in develop mental time, fecundity and adult body size. However, these traits were high ly sensitive to changes in environmental temperatures; and furthermore, sig nificant interactions between population and temperature occurred in all tr aits except for flight capacity of female moths. Thus, phenotypic plasticit y may be another cause of interpopulation variation. The interpopulation va riation for some measured traits was apparently related to climatic differe nces found where the populations originated. Individuals of the populations from the warmer climates tended to develop more slowly at immature stages, producing smaller and less fecund moths but with stronger flight capacity, in comparison to those from the cooler regions. It seems, therefore, that natural populations off. postvittana have evolved different strategies to c ope with local environmental conditions.