Phylogenetic analyses reveal reliable morphological markers to classify mega-diversity in Onthophagini dung beetles (Coleoptera: Scarabaeidae: Scarabaeinae).

Based largely on homoplastic characters of external morphology, the current systematics of the tribe Onthophagini and allied dung beetle lineages is unstable, contradictory, and thus inefficient. A number of recently proposed molecular phylogenies conflict strongly with each other and with formal classification, and none of them provides new tools for the improvement of dung beetle systematics. We explored the source of these inconsistencies by performing an independent, morphology-based phylogenetic analysis of the "Serrophorus complex", one of the most systematically confusing knots among the onthophagines, that involves 52 species from various genera of Onthophagini and allied tribes. The phylogenetic pattern revealed conflicts with existing classifications and with most of the earlier molecular phylogenies. However, it was largely congruent with the molecular phylogeny (Evolution 2005, 59, 1060), using the largest gene sampling thus far. All current competing phylogenetic hypotheses were evaluated against each other, and the degree of their biogeographic plausibility was used as an additional evaluative criterion. Of the 91 morphological characters involved in our analyses, traits belonging to the endophallic sclerites of the aedeagus had a very strong phylogenetic signal. Terminology of these endophallic characters was established and their morphology was studied in detail, illustrated, and presented as a tool for further practical use. The enormous variety of shapes of the lamella copulatrix within the Onthophagini and allies present a methodological problem in character coding for phylogenetic analyses. Based on the performance of alternative coding approaches, it is argued that a seemingly less informative absence/presence coding scheme would be a better choice. The phylogenetic structure of the Serrophorus complex has been largely resolved, and some taxonomic changes improving its systematics are recommended. © The Willi Hennig Society 2011.