A revisionary study of the genus Dasychela (Diptera: Tabanidae) with reference to the evolution of extreme morphologies

Dasychela Enderlein, 1922, the only genus of long-proboscid horse flies in the tribe Diachlorini (subfamily Tabaninae), is revised. The genus contains morphologically distinctive species with extremely long terminal labial palpomeres, long proboscids, and unique trifurcate antennae. Recent studies have shown that long proboscides can indicate specialized pollination biology. Ten valid species are recognized in two subgenera, Dasychela and Triceratomyia. One species new to science is described. Dasychela is endemic to Central and South America. An identification key to species supported by photographs and scanning electron micrographs is presented. Phylogenetic analyses which test the monophyly of Dasychela, the relationships of its species, and the placement of Dasychela in the Diachlorini using morphological and molecular evidence are performed. The phylogeny is the framework for answering questions about the evolution of extreme morphologies in Dasychela. The most probable ancestral states of proboscis, antenna, and palpi morphology are reconstructed using quantitative methods. Ecological and diversification rate shifts associated with these characters are investigated.