Abstract:
Trogidae constitute a monophyletic and biologically unique family within Scarabaeoidea, being the only
keratinophagous group in the superfamily. Traditionally, the family has been divided into three distinctive genera,
Polynoncus Burmeister, Omorgus Erichson and Trox Fabricius. Although the taxonomy of the group is relatively well
studied, changes to the existing classification have recently been proposed and the family as currently constituted has
not been subjected to phylogenetic analyses. Here we present a molecular phylogeny for this cosmopolitan family based
on three partially sequenced gene regions: 16S rRNA, 18S rRNA and 28S rRNA (domain 2). Included in the analyses
are representatives belonging to four of the five extant genera (and three of the four subgenera) from all major
zoogeographic regions, representing about 20%of the known trogid species diversity in the family. Phylogenetic
analyses performed included parsimony and Bayesian inference. We deduce their historical biogeography by using trogid
fossils as calibration points for divergence estimates. Our analyses resolved relationships between and within genera
and subgenera that are largely congruent with existing phylogeny hypotheses based on morphological data. We
recovered four well-supported radiations: Polynoncus, Omorgus, Holarctic Trox and African Phoberus MacLeay. On
the basis of this study, it is proposed that taxonomic changes to the generic classification of the family be made. The
subgenera Trox and Phoberus should be elevated to genera to include the Holarctic and all the Afrotropical species,
respectively, and Afromorgus returned to subgeneric rank. Estimates of divergence time are consistent with a Pangaean
origin of the family in the Early Jurassic. The subsequent diversification of the major lineages is largely attributed to the
break-up of Pangaea and Gondwana in the Middle Jurassic and early Late Cretaceous, respectively.
