Although monographing clades of Therevidae is a major goal of our project, as predicted, difficulties arose early in defining discrete monophyletic units. The family Therevidae had no internal hierarchy except for subfamilial lineages when the project was initiated. An early objective, therefore, was to clarify basal and delineate near-basal clades so that monophyletic groups could be established and monographed. To this end, much progress is being made on a major manuscript by Irwin and Yeates, using 94 adult morphological characters, to generate a phylogeny for 55 in-group taxa (chosen from a world-wide sampling of genera) with 5 out-group taxa. Independently, using a large subset of the same taxa, Wiegmann and Yang produced a phylogeny based on nucleotide sequences of two genes (28S rDNA and EF1a). Dopa decarboxylase and PEPCK genes are being amplified to determine their potential to differentiate among therevid genera and asiloid taxa. The cladistic analyses from morphology and molecular data sets, for the most part, support one another, especially at the basal and near-basal nodes. These two sets of information now permit the selection of discrete monophyletic units to monograph. Not all lineages have been resolved (this proposal points to lineages that remain poorly differentiated and need clarification through added taxa and character analyses).

Students engaged in monographic revisions of specific genera also defined the clade to which that particular genus belonged. No easy task, the genera selected for monography are species-rich, and their near relatives are unknown and potentially from any biogeographic region of the world. Two students hit paydirt in hypothesizing that discovered synapomorphies would define inclusive clades. Gaimari has defined the Tribe Cyclotelini, containing the species-rich genus Ozodiceromyia, and Winterton defined the "Agapophytus Group" within which lies the diverse nominal genus. Holston and Metz are taking the same approach with Thereva and Brachylinga.

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