Relative frequency of amino acid substitutions in single copy and duplicated genes. Ka = Number of amino acid substitutions per amino acid site; Ks = cumulative number of synonymous substitutions per 4-fold degenerative site , i.e. cumulative length of branches leading to either single copy or duplicated genes. Ka / Ks for single copy and duplicated branches calculated for each gene family separately and averaged by molecular function without weighing. Standard errors shown reflect variance among gene families. Red bars: single copy genes in gene families without duplications; orange bars: single copy genes in gene families with duplication; green bars – duplicated genes. Inset: All substitutions and unambiguous substitutions for all gene families combined.