HOST-PLANT EFFECTS ON THE GENETIC-VARIATION AND CORRELATIONS IN THE INDIVIDUAL-PERFORMANCE OF THE GYPSY-MOTH

1. Quantitative genetic analysis of variation in host-use ability was performed in an extremely polyphagous species - the gypsy Moth. Variou s life-history traits were investigated by applying a split-family two -environment experimental design, where 30 full-sibling families were reared on oak and Locust Tree leaves. 2. Feeding on Locust Tree leaves decreased preadult viability, prolonged development time, decreased p upal mass both in males and females, and decreased reproductive effort in females. 3. The majority of broad-sense heritabilities did not cha nge across host plants. 4. Significant expression of genetic variation in diet breadth was observed for development time and pupal mass both in males and females, but not for female reproductive effort traits. The heritabilities of plasticities were, on average, lower than herita bilities of the traits themselves. 5. The majority of genetic correlat ions between the host plants were significantly positive. The only tra de-off was found between reciprocal value of reproductive index and th e average mass of a fertilized egg within oak. This means that selecti on for the decrease in relative reproductive investment (under starvat ion during gradation) will be followed by laying larger eggs. Given th at the Gypsy Moth has a cyclic population dynamics, this negative gene tic correlation could have a role in maintaining genetic variability i n this species.