Figure 1.

Quantification of orthologous gene losses in insects and vertebrates. (a) The phylogenetic relations among the organisms are illustrated by the tree, with branch length proportional to the rate of amino acid substitutions estimated using the maximum-likelihood approach. The number of orthologous groups lost on the internal phylogenetic branches were inferred using the Dollo parsimony principle and are shown on the phylogenetic tree above branches for the I/V fraction, and below branches for the P fraction. *The presence in two species was sufficient to infer losses of I/V orthologous groups. (b) The number of orthologous group losses in the five main categories: U, universal single-copy genes (blue, present in all species except the one in question); N, universal multiple-copy genes (orange, present in at least nine species); P, patchy orthologs (yellow, present in both phyla in at least three species, in one or multiple copies); I/V, insect- or vertebrate-specific orthologous groups (present only in insects (green) or vertebrates (violet), in at least three species. The dark parts of the bars depict the number of contemporarily present orthologous groups, and the light parts depict the number of inferred losses. AGAM, Anopheles gambiae; AAEG, Aedes aegypti; DMEL, Drosophila melanogaster; TCAS, Tribolium castaneum; AMEL, Apis meliferia; HSAP, Homo sapiens; MMUS, Mus musculus; MDOM, Monodelphis domestica; GGAL, Gallus gallus; TNIG, Tetraodon nigroviridis.