Quantitative genetics, development, and physiological adaptation in host strains of fall armyworm

Abstract

Two genetically differentiated host strains of Spodoptera frugiperda were reared on their own and each other's host plants. Larval host had a greater impact on development in the rice strain than in the corn strain, indicating that physiology could have facilitated specialization in one strain but not the other. Consequently, behavioral mechanisms are also likely to be important in the maintenance of host specificity. Comparison between strains indicated significant differences in the rate at which larvae gained weight. Because this character had consistently high heritabilities, genetic differentiation in development is indicated. Genotypic performance on one host was apparently not indicative of performance on the other. Each strain exhibited genetic variation that would facilitate host-associated divergence and adaptation if coupled with a mechanism that reduced gene flow between hosts. Significant genetic correlations between several characters were detected when strains were reared on their natural hosts but not when they were reared on nonnatural hosts: feeding on novel hosts caused developmental uncoupling of characters. Release from genetic constraints could provide a mechanism for physiological adjustments to newly occupied habitats. -from Author