Additional molecular evidence to support a sister taxon relationship between Heligmosomoidea and Molineoidea nematodes (Trichostrongylina).

Sequences of the first and second internal transcribed spacers of the ribosomal DNA were used to infer the evolutionary relationships of 19 species of parasitic nematode belonging to three superfamilies, Trichostrongyloidea, Molineoidea and Heligmosomoidea, within the sub-order Trichostrongylina. Analyses using maximum parsimony, maximum likelihood and neighbor-joining methods revealed strong statistical support for monophyly of each superfamily as defined on morphological criteria. Furthermore, in most analyses, there was also strong support for a sister taxon relationship between the Molineoidea and Heligmosomoidea, which supports the findings of a previous study based on partial LSU rDNA sequence data.