Fig. 3. Sister diversity analysis of 5402 phylogenetic trees reveals Clostridia is the most ancestral group.

Sister diversity (maximum number of different groups in the sister clade) for each group (rows) for 5402 trees with at least six groups (columns). An illustrative tree portrays the question asked in the analyses, where the yellow group is the one with the highest sister diversity score and therefore inferred as most ancestral.