THE GENETICS OF PHENOTYPIC PLASTICITY IN A COLONIZING POPULATION OF THE LADYBIRD BEETLE, HARMONIA-AXYRIDIS

We investigated the degree to which families of a colonizing ladybird beetle, Harmonia axyridis, differed in their phenotypic responses to f amiliar vs. novel food types using a split-brood full-sib design. Deve lopment time, adult size, and two measures of colour were significantl y affected by diet. All traits measured were under some degree of gene tic control. Significant levels of genetic variation existed in phenot ypic plasticity for development time and adult size, but not for two m easures of colour. Genetic correlations were found between several tra its within single environments but no significant cross-environment ge netic correlations were detected. We concluded that: (1) plasticity in development time and adult size may evolve given appropriate selectio n pressure; (2) plasticity in the two measures of colour cannot evolve owing to a lack of genetic variation; and (3) colonization of H. axyr idis is associated with plasticity, though it is not clear that coloni zation events actively select for change in levels of plasticity.