A simple model of the relationship between asymmetry and developmental stability

Abstract

The relationship between developmental stability and morphological asymmetry is derived under the standard view that structures on each side of an individual develop independently and are normally distributed. I use developmental variance of sizes of parts, V(D), as the converse of developmental stability, and assume that VD follows a gamma distribution. Repeatability of asymmetry, a measure of how informative asymmetry is about V(D), is quite insensitive to the variance in V(D), for example only reaching 20% when the coefficient of variation of V(D) is 100%. The coefficient of variation of asymmetry, CV(FA), also increases very slowly with increasing population variation in V(D). CV(FA) values from empirical data are sometimes over 100%, implying that developmental stability is sometimes more variable than any previously studied type of trait. This result suggests that alternatives to this model may be needed.