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.

Phylogeny of the African ball-rolling dung beetle genus Epirinus Reiche (Coleoptera:Scarabaeidae:Scarabaeinae)

“…Our assessment of food relocation behaviour confirms that the genus Epirinus appears to be a 'true roller'. It also appears that these species may exhibit plasticity in their food relocation behaviour as seen in other dung beetle taxa (Philips et al 2004 and references therein). Admittedly, most dung beetles show selectivity for particular dung based on qualities such as dropping size, texture and fibre content (Rahagalala et al 2009) but they may also be opportunists that exhibit different behaviours to suit their environment.…”

“…Monophyly of the genus was supported. However, as in other scarabaeines (Philips et al 2004), there was a high degree of homoplasy in the morphological characters that were used.…”

“…Recent phylogenetic studies have postulated that in Scarabaeinae rolling balls of dung evolved independently several times (Philips et al 2004;Monaghan et al 2007). Sole and Scholtz (2010) tried to "tease apart the different taxa of tunnellers and rollers" concluding that within the African Canthonini and Dichotomiini Epirinus appeared to be the most basal of all rollers.…”

“…Although the global Scarabaeinae dung beetle fauna is divided into 12 tribes (Hanski and Cambefort 1991), some of these divisions lack phylogenetic support (Medina et al 2003;Philips et al 2004;Monaghan et al 2007;Davis et al 2008;Sole and Scholtz 2010). The current classification is considered to be based on two large 'monophyletic' groups (Cambefort 1991): 1), one containing six tribes of "tunnellers" with Dichotomiini being basal; and 2), the other consisting of six tribes of "rollers"…”

“…Philips et al (2004) used 200 morphological characters in their analysis which included representative genera from all 12 tribes and concluded that the ancestral Scarabaeinae was a tunneller and that rolling has evolved independently a number of times. Monaghan et al (2007) performed an extensive molecular phylogenetic analysis and came to several of the same general conclusions as those of Philips et al (2004). One of these was that the basal extant dung beetle groups are African genera currently placed in the Canthonini and Dichotomiini.…”