Fig. 2

Maximum likelihood (ML) phylogenetic tree of the genus Spirostomum. The topology is based on 136 18S-ITS-28S rRNA gene operon sequences (2,459 bp) and the TIM2e + I + G4 model. Monophyletic clades were collapsed for clarity (see also Additional file 1: Fig. S3). Numbers in parentheses indicate the total number of specimens (in black font) in a lineage and the number of specimens with transcriptomic data used for phylogenomic analyses (in bold orange font). Numbers at nodes are ML bootstrap values and SH-aLRT from 1,000 replicates. Red solid circle on nodes indicates maximum support. The scale bar corresponds to the number of nucleotide substitutions