Morphology-­‐based phylogenies in Onthophagus species of d’Orbigny‘s 32 group (Coleoptera, Scarabaeidae)

We present a first phylogenetic hypothesis for an african Onthophagini group, defined by H. d’Orbigny as the 32 group of the genus Onthophagus, comprising more than 2300 species, characterized by problematic, complicated and often not-resolved taxonomy. This group includes six species, namely O. acutus d’Orb. , O. bituberculatus Ol., O. depressus Har., O. fallax d’Orb., O. laceratus Gerst. and O. pallens d’Orb. The phylogeny was based on the combination of morphological characters, validated with a study of more than a thousand specimens. External morphology, wing pattern, mouthparts, particularly the epipharynx, male and female genitalia, genital segment, and metaendosternite, provided a large characters dataset. Digitonthophagus bonasus (F.) was used as outgroup taxon. Phylogenetic analyses were based on Maximum Parsimony and Bayesian Inference criteria. Species distributions were ascertained by georeferencing the collection localities. Geographical data were integrated with phylogeny and processed with dispersal vicariance analysis (RASP). The analysis of the overall dataset has produced a single phylogenetic tree with high goodness values. The cladogram shows that, contrary to what commonly assumed to date, the species of the 32 group do not constitute a homogeneous group, because there are two distinct lines, not phylogenetically close. The first line includes 5 taxa clustered in a resolved, well isolated and homogeneous group, especially with regard to genitals of both sexes, while the second line include O.pallens only. This species was probably added to the 32 group by virtue of convergent homoplastic characters, but our analysis suggests that the affinity with the other lineage is low.