PARASITISM AND DEVELOPMENTAL INSTABILITY OF HOSTS - A REVIEW

Developmental stability reflects the ability of a genotype to undergo stable development of a phenotype under given environmental conditions . Deviations from developmental stability arise from the disruptive ef fects of a wide range of environmental and genetic stresses, and such deviations are usually measured in terms of fluctuating asymmetry and phenodeviants. In this review, evidence is presented for a general rel ationship between health and developmental stability since the prevale nce and the intensity of infections with parasites generally are assoc iated with elevated developmental instability. The only exception is d evelopmental stability in secondary sexual characters sometimes being positively associated with an increased frequency of venereal disease. Four studies have reported an elevated susceptibility to parasites am ong individuals with high levels of developmental instability. The cau se of the positive relationships between parasitism and developmental instability may be either the generally poor condition of developmenta lly unstable individuals, or such individuals having genetically deter mined poor resistance to parasites as also reflected in an elevated le vel of developmental instability. The general relationship between par asitism and developmental instability has important implications for s tudies of parasite-host relationships in general and for conservation biology in particular.