Figure 4

Evolutionary scenarios in phylogenetic trees. The different kinds of evolutionary scenarios seen in phylogenetic trees are shown. A) Species tree showing the evolutionary relationship between the species, 1, 2, 3 and 4. B) A species-specific gain of genes appears as a clade including a single homolog from one species and multiple homologs from the other. Phylogeny between genes from species 1, 2, 3 and 4, respectively is shown. Gene gain in species 4 is observed. C) Species-specific gene loss appears as the absence of a corresponding ortholog for one species on the tree and is deduced from the evolutionary relationships of the species considered with the other species. Gene loss occurred in species 3.