Effect of sequence length on tree topology

Phylogenetic trees inferred with full-length 16S rRNA sequences (left) and sequences truncated to omit E. coli positions 1-359 (right). The organisms cover the entire range of the cyanobacterial phylum and include strains related at the levels of species, genus, family and order. Those that may be subject to unusual evolutionary constraints (such as obligate endosymbionts and the Prochlorococcus spp.) were omitted. Strains or clusters coloured red indicate dramatic topological changes; those coloured blue have changed position only within their clade.