Parsimonious scenarios of loss and emergence of genes (KOGs) in eukaryotic evolution. (a) The coelomate topology of the phylogenetic tree of the eukaryotic crown group. (b) The ecdysozoan topology of the phylogenetic tree of the eukaryotic crown group. The numbers in boxes indicate the inferred number of KOGs in the respective ancestral forms. The numbers next to branches indicate the number of gene gains (emergence of KOGs) (numerator) and gene (KOG) losses (denominator) associated with the respective branches; a dash indicates that the number of losses for a given branch could not be determined. Proteins from each genome that did not belong to KOGs as well as LSEs were counted as gains on the terminal branches. The species abbreviations are as in Figure 1.