Phylogenetic assessment of the Branchiobdellidae (Annelida, Clitellata) using 18S rDNA, mitochondrial cytochrome c oxidase subunit I and morphological characters

Using 18S rDNA, mitochondrial cytochrome c oxidase subunit I and morphologi cal characters, the Branchiobdellidae (Annelida, Clitellata) were shown to form a monophyletic group distinct from the leeches using two distant 'olig ochaetes' as outgroups. The study used 20 branchiobdellid species from 14 g enera in four subfamilies with these representing each of the taxon's three distributional regions in the Holarctic realm. No monophyletic groups were found using the gene sequence data that related to either geographical reg ions or currently recognized subfamilies. However, two monophyletic groups were strongly supported; the two European species of Branchiobdella and the combination of Sathodrilus attenuatus and Xironogiton victoriensis. The la tter pair is taxonomically diverse, but sympatric on Signal crayfish, Pacif astacus leniusculus, in California, USA.