Insights into the evolutionary history of Indo-Pacific bloodfeeding terrestrial leeches (Hirudinida : Arhynchobdellida : Haemadipisdae)

Haemadipsidae is a clade of notorious bloodfeeding annelids adapted to tropical and sub-tropical rainforests found throughout the Indo-Pacific. This family traditionally includes duognathous (two-jawed) endemics, each placed in their own genus, from continental and volcanic islands including: Australia, Indonesia, Madagascar, Papua New Guinea, Philippines, Seychelles, and South Pacific islands, while trignathous (three-jawed) Tritetrabdella species and the speciose Haemadipsa are exclusive to the Indian subcontinent ranging into east and south-east Asia. One of the more compelling aspects of haemadipsids is their distribution on post-Gondwanan landmasses. In this study, the phylogenetic relationships, taxonomy and biogeographic patterns of Haemadipsidae were examined. Over 5 kb of sequence data from three genes (nuclear 18S rDNA and 28S rDNA and mitochondrial COI) for 37 haemadipsid exemplars, representing 12 of the 15 recognised genera, were analysed under the criteria of maximum parsimony and Bayesian inference. The results show that widespread duognathous species form a monophyletic group derived from trignathous ancestry and are sister to a new trignathous clade for Haemadipsidae. This phylogenetic hypothesis rejected Gondwanan vicariance as an explanation for the diversification of haemadipsids. Haemadipsidae is accepted as the formal name for these Indo-Pacific leeches. Whereas the subdivisions Haemadipsinae and Domanibdellinae are clarified, there is a need to establish a new subfamily, Tritetrabdellinae, for the newly identified trignathous clade that is sister to Domanibdellinae. This study provides a basis for continued elucidation of the evolutionary relationships and classification of these terrestrial annelids.