Fig. 1

The number of phenotypic categories and the rate of protein evolution. The number of phenotypes for individual proteins is measured by the number of distinct categories of RNAi phenotypes that are significantly affected by knockdown of the corresponding gene. The box plots show the distribution of direction of selection (DoS) values for three different categories: genes that significantly affect one, two, and three different phenotypes upon RNAi knockdown. A positive DoS value indicate an excess of the proportion of substitutions in D. melanogaster that are nonsynonymous substitutions relative to the proportion of polymorphisms that are nonsynonymous. The mean DoS for genes involved in three categories of phenotype is significantly more positive compared to genes involved in either one or two phenotypic categories