THE GENETIC-BASIS OF DEVELOPMENTAL STABILITY .2. ASYMMETRY OF EXTREME PHENOTYPES REVISITED

Soule and Cuzin-Roudy proposed that individuals lying in the extremes of the phenotypic distribution for certain characters (complex characters with high heritability) will be developmentally more unstable for such characters than individuals in the center of the distribution. This result was interpreted as occurring because of greater levels of homozygosity in extreme individuals for a given character than in modal individuals. Potentially confusing mathematical procedures used in their original study led to a reexamination of this ''outgroup'' effect utilizing existing data sets from four insect species. Although results confirm the presence of a significant outgroup effect for some characters and some species, the basis of the phenomenon is reinterpreted in terms of a fitness-dependent character-specific model of stability.