Figure 2

Estimated minimal evolutionary age of S100 family members. Open rectangles represent the gene gain events in each lineage, and black boxes represent the gene loss events. Inside each box is the name of the respective gene(s). A duplication event leading to a gene pair is indicated by a common rectangle. The major phylogenetic transitions are indicated: bo/nobo, bony fish/cartilaginous fish; ac/sa, actinopterygian/sarcopterygian split; os/neo, ostariophysii/neoteleostei segregation. The maximum parsimony principle was followed for construction of this scheme, i.e. minimal gene losses and gene gains were assumed. Thus gene gains are depicted at the last possible stage before additional gains would become necessary for explanation, but may in fact have occurred earlier, accompanied by gene loss in some lineages.