A phylogenetic analysis of dung beetles (Scarabaeinae : Scarabaeidae): unrolling an evolutionary history

Abstract

The phylogeny of the Scarabaeinae, the largest and most important group of dung feeding beetles, is hypothesised based on 200 morphological characters of 50 taxa, representing nearly one quarter of the known genera. We present a drastically different picture of evolution of this highly successful group of beetles than those previously proposed. It is apparent that gross morphology is correlated with either rolling or tunnelling but does not accurately reflect evolutionary history. Results indicate that there are not two separate clades of dung beetles, the rollers and tunnellers, but that rolling behaviour has evolved several times from ancestral tunnellers. The Dichotomiini, Canthonini, and Coprini are poly- or paraphyletic, whereas each of the remaining nine tribes appear as well supported monophyletic clades (the monophyly of the Gymnopleurini was not tested). The genera traditionally included in the Dichotomiini are the oldest and most basal lineages and all other clades, including those of the Canthonini, evolved from ancestral dichotomiine lineages either directly or indirectly. New interpretations of the evolution of rolling, its possible loss, nesting and feeding behaviours, and future changes in classification are discussed. Evidence supports the origin of the Scarabaeinae before the Tertiary and subsequent vicariance of many clades via the breakup of Gondwanaland.