Genetic analysis of larval survival and larval growth of two populations of Leptinotarsa decemlineata on tomato

The genetics of adaptation to tomato in Leptinotarsa decemlineata (Say) wer e investigated in reciprocal F-1, F-2, and backcross populations generated from crosses between beetles from a tomato adapted population and from a po pulation that was poorly adapted to tomato. Larvae from the parent and test populations were reared on tomato for four days, after which survivorship and larval weights were recorded. Most results indicate that differences in larval growth and survival on tomato between the parent populations are la rgely determined by autosomal, polygenic mechanisms, the inheritance of whi ch involves a significant dominance component. However, results from F-2 cr osses are not consistent with this conclusion. A significant difference in larval weights, but not in survival, between reciprocal F-1 populations in an analysis of combined data from four separate experiments suggests that m aternal cytoplasmic effects may contribute to differences in larval perform ance on tomato between the adapted and unadapted populations. The unusual r esults obtained from F-2 crosses in this study are not atypical of results from previous studies of the genetics of adaptation to host plants by the C olorado potato beetle. Host plant adaptation by Colorado potato beetles may therefore involve unusual genetic mechanisms that are not easily assessed by classical Mendelian analysis.