Enzyme heterozygosity and developmental stability

Regular development of morphology is challenged by any environmental influence that draines energy from developing individuals. For half a century biologist have recognized that developmental stability, measured as the capability to regulate development of normal morphological structures, is influenced by genetic variation. This review considers the influence of enzyme polymorphism upon developmental stability. Empirical studies in a wide variety of animals have reported morphological variability and bilateral assymmetry to decrase with the heterozygosity of enzyme polymorphism. A controversy focuses on the question of whether the enzymes are neutral markers that either reveal variation in levels of inbreeding or are in linkage disequilibrium with genes directly influencing development. Another controversy focuses on whether the relationships between enzyme heterozygosity and development stability, most commonly reported in poikilotherms, will also be found homeotherms. These controversies are addressed by considering recent empirical studies of enzyme polymorphism and developmental stability.