Ortholog grouping. (a) Phyletic grouping of Ich genes with previously grouped orthologs from other species. Numbers in parentheses indicate the total number of ortholog groups to which the respective genes belong. (b) Shared orthology between the three ciliate genomes. The numbers depict the total number of ortholog groups in each category. The numbers within the brackets indicate ortholog groups specific for Tetrahymena only and accordingly there are 341 ciliate specific ortholog groups shared with all 3 ciliates compared here. See Additional file 6 for more details regarding shared orthology between the three ciliates.