Phylogenetic relationships within the kinetoplastid flagellates were inferred from
comparisons of small-subunit ribosomal RNA gene sequences. These included three new
gene sequences from Cryptobia bullocki, (2091 bp), Cryptobia catostomi (2090 bp),
and Cryptobia salmositica (2091 bp). Trees produced using maximum parsimony and distance-matrix
methods (least squares and neighbor-joining) demonstrated with strong bootstrap support,
that the kinetoplastids are a monophyletic group divided into two major lineages consistent
with the two suborders, Trypanosomatina and Bodonina. Within the trypanosomatid clade,
the genus Trypanosoma is a monophyletic group that divides into two groups, the salivarian
trypanosomes and the stercorarian trypanosomes. Dimastigella and Rhynchobodo, currently
classified in the Bodonina, are basal to the trypanosomatid-bodonid clade, suggesting
that the suborder Bodonina is paraphyletic. Further, Trypanoplasma borreli grouped
within the Cryptobia clade, and was more closely related to C. salmositica than to
either C. bullocki or C. catostomi. This new molecular evidence, coupled with morphological
similarities of the two genera, again calls into question the validity of the genus
Trypanoplasma.