Reconstruction of ancestral gene repertoires in the evolutionary history of A46 and related families. The number in every node represents the inferred or real number of groups of orthologues present in each genome. This number was inferred for ancestral species by the maximum likelihood method implemented in the Count program . The background colour of the number indicates the kind of variation in the gene content since the preceding node: green for nodes with a net gene gain, red for nodes with a net gene loss, and grey if the gene content remained unchanged. The tree contains a representative strain for every species of the subfamily Chordopoxvirinae with a completely sequenced genome and is based on a maximum likelihood phylogenetic tree (Additional File 3). Species/strain names as in Figures 1 and 2; TATV-DAH68, Taterapox virus strain Dahomey 1968; CMLV-CMS, Camelpox virus strain CMS; VARV-IND3_1967, Variola virus strain India 3 Major 1967; CPXV-GRI, Cowpox virus strain GRI-90; MPXV-SLE, Monkeypox virus strain Sierra Leone; YMTV-Amano, Yaba monkey tumor virus strain Amano; RFV-Kas, Rabbit fibroma virus strain Kasza; SPPV-A, Sheeppox virus strain A; GTPV-G20LKV, Goatpox virus strain G20-LKV; BPSV-AR02, Bovine papular stomatitis virus strain BV-AR02; ORFV-NZ2, Orf virus strain NZ2; MOCV-st1, Molluscum contagiosum virus strain subtype 1; CNPV-VR111, Canarypox virus strain ATCC VR111; FWPV-Iowa, Fowlpox virus strain Iowa; CRV-ZWE, Crocodilepox virus strain Zimbabwe.