Bayesian phylogenetic tree of Trichuris based on concatenated ITS 1 and ITS 2 rDNA sequences.

18S, ITS 1 (895 bp), and 5.8S, ITS 2, 28S (486 bp) sequences were concatenated, and regions of ambiguous alignment removed in Gblocks. Phylogenetic relationships were inferred using MrBayes, with newly generated sequences clustering in three groups: Group 1 (2 human samples), Group 2 (4 black-and-white colobus and 1 red colobus samples), and Group 3 (7 blue monkey, 9 black-and-white colobus, 4 chimpanzee, 8 human, 4 grey-cheeked mangabey, 4 l'hoest monkey, 8 olive baboon, 10 red colobus, and 12 red-tailed guenon samples). Posterior clade probabilities are shown next to branches. Reference sequences (T. trichiura, T suis) and outgroups (T. discolor, T. ovis, T. skrjabini, T. sp, T. vulpis and Trichinella spiralis) are italicized, with GenBank accession numbers included in parenthesis. Scale bar indicates nucleotide substitutions per site.