The austral horse fly genus Scaptia (Diptera: Tabanidae): monophyletic clade or taxonomic dumping ground?

Horse flies are considered significant pests due to their blood-feeding and transmission of diseases to both humans and livestock, but also have a beneficial role in the pollination of plants. The horse fly genus Scaptia has an exclusively austral distribution occurring predominantly in Australia, with smaller diversifications in New Zealand, New Guinea and South America. Although the taxonomy of Scaptia is quite mature, the systematics of the group is still largely unknown. A 6KB molecular data set of COI, COII, 28S, AATS and CAD was combined with 30 morphological characters. Results indicate that the genus Scaptia is in fact paraphyletic and comprises distinct monophyletic subgenera, that we recommend be raised to genus level. Interestingly, the subgenus S. (Pseudoscione) formed three divergent monophyletic groups that are isolated on Australia, New Zealand and South America, respectively. The phylogeny suggests that Scaptia should be divided into as many as 11 genera. Divergence time estimation using the molecular data calibrated with the fossil record suggests that the current biogeography of Scaptia is most likely caused by vicariance.