Phylogenetic relationships among Onychophora from Australasia inferred from the mitochondrial cytochrome oxidase subunit I gene

Nucleotide sequence variation in a region of the mitochondrial cytochrome o xidase subunit I(COI) gene (456 bp) was examined for 26 onychophorans repre senting 15 genera of the family Peripatopsidae from Australasia. Sequence a nalysis revealed high intergeneric COI sequence divergence (up to 20.6% cor rected) but low amino acid substitution rates, with high levels of transiti onal saturation evident. Among unambiguously alignable sequences, parsimony and distance analyses revealed a broadly congruent tree topology, robust t o various algorithms and statistical analysis, There are two major grouping s. One, largely unresolved, consists entirely of Australian mainland taxa. The other, for which there is convincing support, includes all of the New Z ealand and Tasmanian taxa together with one mainland Australian species. In respect of the two major groupings, this topology is consistent with previ ous morphologically based phylogenies and provides further evidence for an ancient radiation within the mainland Australian Onychophora, The biogeogra phic implications of the close affinities revealed between the Tasmanian an d New Zealand taxa are discussed. (C) 1998 Academic Press.