A simple model of the relationship between asymmetry and developmental stability

The relationship between developmental stability and morphological asymmetr y is derived under the standard view that structures on each side of an ind ividual develop independently and are normally distributed. I use developme ntal variance of sizes of parts, V-D, as the converse of developmental stab ility, and assume that V-D follows a gamma distribution. Repeatability of a symmetry, a measure of how informative asymmetry is about V-D, is quite ins ensitive to the variance in V-D, for example only reaching 20% when the coe fficient of variation of V-D is 100%. The coefficient of variation of asymm etry, CVFA, also increases very slowly with increasing population variation in V-D. CVFA 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 mode l may be needed.