An experimental analysis of the relationships between fitness components and malic enzyme genotypes in Tribolium confusum.

The hypothesis that natural selection is capable of maintaining allozyme variation in natural populations was tested using a species of flour beetles, Tribolium confusum. We selected a polymorphic locus (a locus encoding variation for malic enzyme) in an experimental population of T. confusum and scored the genotypes at this locus for a series of fitness components on different flour types. Measurements included survival rate, development time, fecundity, and rate of egg cannibalism. Flour type had significant effects on most traits. Significant differences among genotypes for fecundity and rates of egg cannibalism and the presence of genotype x flour type interactions for development time were demonstrated. Thus, changes in allele frequencies at the malic enzyme locus could in part be under the influence of natural selection. The existence of genotype x flour type interactions suggests that environmental heterogeneity could maintain allozyme variation at the malic enzyme locus.