Quantitative genetic analysis of fitness-related traits in the soldier-producing aphid, Pseudoregma bambucicola (Homoptera: Aphididae): Genetic variation and costs of soldier production

Abstract

Genetic bases of several traits of the soldier-producing aphid Pseudoregma bambucicola (larval period, reproductive age, adult body size, colony fitness, and proportions of adults, alates and soldiers) were examined by quantitative genetic analyses with particular reference to colony-level stabilizing selection on soldier proportion. Five aphid clones were grown on Bambusa multiplex shoots that were clonal but of different ages. The age of the shoot was regarded as an environmental factor affecting aphid fitness. Mixed model ANOVA detected no significant effects of genotype and genotype-environment interaction on colony fitness, whereas the fitness was higher on younger hosts. This suggests that no single clone exceeds other clones in fitness in all environments. While a significantly larger amount of genotypic variance was detected in body size and adult proportion, the soldier proportion exhibited less genotypic variance. This result suggests that the soldier proportion is intimately associated with fitness and is under strict stabilizing selection. A negative genetic correlation was detected between soldier proportion and colony growth. This also suggests that stabilizing selection has operated on soldier proportion so as to maintain eusociality in P. bambucicola that lacks kin recognition.