Figure 1

Comparisons of evolutionary changes in the 18S and the ITS1 sequence. Left tree (black): Maximum likelihood (ML) phylogeny of cercomonad 18S rDNA sequences calculated from an alignment of 15 sequences and 213 nucleotide positions from the hypervariable V4 region. Right tree (grey): ML phylogeny of corresponding ITS1 rDNA (213 positions). Branch lengths and scale bars standardised to illustrate the much greater evolutionary rate of ITS1 than even the most hypervariable 18S rDNA region. Equivalent parsimony analyses using gaps as a 5th character (not shown) showed a parsimony score of 367 (minimum changes) for ITS1 and 120 for the V4 18S rDNA region. Cultures used for ecological and phenotypic character experiments (Table 2) marked by circles.