The evolution of Diachlorini (Diptera: Tabanidae) based on phylogenetic analyses using morphological and molecular data

Diachlorini is the most genus-rich and morphologically varied tribe in Tabanidae, a diverse and well-known family of lower brachyceran Diptera. Horse flies can be a nuisance and transmit disease to humans and livestock and are also useful models in the study of pollinator coevolution. Dasychela, the genus with the longest proboscides of any non-pangoniine horse fly, and Lepiselaga, the only known phytophagous horse fly, are both diachlorines. The phylogenetic relationships among subgroups of Diachlorini are controversial and the group is never supported as monophyletic in phylogenetic studies. Previous attempts to restructure Diachlorini have either been in a pre-phylogenetic framework or used few variable characters. Using data from mitochondrial cytochrome oxidase 1, ribosomal 28s, and three nuclear genes, and 50 external adult morphological characters, a robust phylogenetic hypothesis is proposed for Diachlorini. Morphological homoplasy is rampant and several deep divergences are poorly resolved, suggesting ancient radiations of horse flies which may coincide with biogeographical events. A more stable classification scheme is proposed based on natural groups identified by this study.