Systematics

Abstract

Hennig’s (1966) concept of hierarchies of monophyletic taxons based on common ancestors (with plesiomorphies or retained primitive, ancestral characters) and shared synapomorphies (homologous shared characters inferred to have been present in the nearest common ancestor but not in earlier ancestors nor in the taxa outside this group), has provided the theoretical basis for taxa formation. During the first decades following its proposal, it resulted in the establishment of cladistic trees where recency of common ancestry is the sole criterion for grouping of the taxa. The problem of ranking taxa and tree formation in a Darwinian evolutionary context was the next scientific step (Eldridge and Cracraft 1980). Opinions about what different nodes represent, how to deal with branch lengths, and how to rank monophyletic entities, have become part of a scientific field of its own (Britton et al. 2007). Applying both morphologic and genetic taxonomic methods, and working with different groups of characters to reveal evolutionary relationships between insect orders or families as monophyletic groups, is now becoming standard. In the new millennium this work has resulted in several new hypotheses of phylogenetic trees of Insecta. Wheeler et al. (2001) established the relationship between Diptera and Strepsiptera. Grimaldi and Engel (2005) in their comprehensive work on extinct and extant Insecta, summarized different hypotheses for Diptera. They accepted five suborders of Lower Diptera (Nematocera): Tipulomorpha, Psychodomorpha, Culicomorpha, Blephariceromorpha and Bibionomorpha. They placed Anisopodidae as a sistergroup to Brachycera (all higher Diptera) and discarded Nematocera as a paraphyletic group (including a most recent common ancestor and some, but not all, of it descendants). This view has been strongly advocated by Amorim et al. (2006). They recognised seven suborders/infraorders instead of Nematocera and added Brachycera as the eighth suborder/infraorder for the rest of the Diptera.