Scarabaeoidea Phylogenetics and Classification

Smith, Andrew B. T., Hawks, David C. & Heraty, John M., 2006, An Overview Of The Classification And Evolution Of The Major Scarab Beetle Clades (Coleoptera: Scarabaeoidea) Based On Preliminary Molecular Analyses, The Coleopterists Bulletin (mo 5) 60, pp. 35-46 : 38

Higher Scarabaeoidea Phylogenetics and Classification

Although there are several scarab classification schemes currently used in the literature, it is desirable to focus towards a universal system of classification that is based on evolutionary relationships while respecting historical precedence. It also is appropriate to harmonize Scarabaeoidea classification with that of other superfamilies of Coleoptera . With these goals in mind, the scarab beetle classification schemes of Lawrence and Newton (1995) and Browne and Scholtz (1995, 1999) have been set as the standard for scarab taxonomists over the past decade. This 12–14 family classification system is based on phylogenetic analyses and is constructed in the context of other Coleoptera . Our research on the molecular phylogenetics of scarab beetles gives us the opportunity to scrutinize this classification system using a new data set.

The 12–14 family Scarabaeoidea classification system of Lawrence and Newton (1995) and Browne and Scholtz (1995, 1999) place major clades such as Geotrupidae , Passalidae , Lucanidae , Trogidae , and Hybosoridae in separate families while lumping all of the dung scarabs ( Aphodiinae , Scarabaeinae , etc.) and phytophagous scarabs ( Melolonthinae , Cetoniinae , Rutelinae , Dynastinae , etc.) into the family Scarabaeidae . Scholtz and Chown (1995) provided discussion and justification for doing this by using the phylogeny of Browne and Scholtz (1995) and the known fossil record of scarabs to hypothesize that this entire clade evolved during the Tertiary. Scholtz and Chown (1995) attempted to stabilize Scarabaeoidea classification by considering the major clades that originated in the Mesozoic as families while those that originated in the Tertiary were relegated to subfamily or tribal rank. However, Krell (2000), Davis et al. (2002), Smith (2002), Philips et al. (2004), and others have since provided biogeographical or fossil evidence that the dung scarab clade and the phytophagous scarab clade both originated and diversified in the Cretaceous, not the Tertiary. Based on the contradictions in the date of origin for some lineages of scarab beetles and the availability of a new and more detailed phylogenetic analysis for the superfamily, we feel that it is appropriate and possible to re-examine and modify higher scarabaeoid classification.

Below, each of the major clades of Scarabaeoidea are listed and discussed in the context of our preliminary molecular phylogenetic analyses. Comparisons are made to previous phylogenetic hypotheses and to some of the historical placements of some groups. We also discuss some classification changes that seem to be necessary based on our results. These changes will improve higher scarabaeoid classification by making it more parallel to the evolution of the major scarab clades. A preliminary, simplified tree with hypothetical relationships of major scarabaeoid groups (families and a few selected subfamilies) is presented in ( Fig. 1 ). Weakly supported branches are indicated with thin lines, moderately to strongly supported branches are indicated with thick lines.

Figures

Fig. 1. Preliminary phylogenetic tree of the Scarabaeoidea based on molecular data. Collapsed branches indicate no support or very weak support in all analyses, thin branches indicate weak bootstrap support, and thick branches indicate strong support. Bootstrap values are from an analysis of the entire dataset. Terminal taxa depicted represent 4–140 species that were sequenced.