DIVERSITY IN THE WEAPONS OF SEXUAL SELECTION: HORN EVOLUTION IN THE BEETLE GENUS ONTHOPHAGUS (COLEOPTERA: SCARABAEIDAE)

Both ornaments and weapons of sexual selection frequently exhibit prolific interspecific diversity of form. Yet, most studies of this diversity have focused on ornaments involved with female mate choice, rather than on the weapons of male competition. With few exceptions, the mechanisms of divergenc...

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Bibliographic Details
Published in:Evolution 2005-05, Vol.59 (5), p.1060-1084
Main Authors: Emlen, Douglas J, Marangelo, Jennifer, Ball, Bernard, Cunningham, Clifford W
Format: Article
Language:English
Subjects:
Adaptation, Biological
Adaptive radiation
Animal horns
Animal reproduction
Animals
Bayes Theorem
beetle horns
Beetles
Biological Evolution
Biological taxonomies
character divergence
Coleoptera
Coleoptera - anatomy & histology
Coleoptera - genetics
DNA Primers
DNA, Mitochondrial - genetics
Dung beetles
Environment
Evolution
Female
Female animals
Genetic diversity
Horns - anatomy & histology
Insects
Likelihood Functions
Male
Male animals
male competition
Models, Genetic
Onthophagus
Phylogeny
REGULAR ARTICLES
RNA, Ribosomal, 28S - genetics
Scarabaeidae
Selection, Genetic
Sequence Analysis, DNA
Sex Characteristics
Sexual selection
Species Specificity
Weapons
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Summary:Both ornaments and weapons of sexual selection frequently exhibit prolific interspecific diversity of form. Yet, most studies of this diversity have focused on ornaments involved with female mate choice, rather than on the weapons of male competition. With few exceptions, the mechanisms of divergence in weapon morphology remain largely unexplored. Here, we characterize the evolutionary radiation of one type of weapon: beetle horns. We use partial sequences from four nuclear and three mitochondrial genes to develop a phylogenetic hypothesis for a worldwide sample of 48 species from the dung beetle genus Onthophagus (Coleoptera: Scarabaeidae). We then use these data to test for multiple evolutionary origins of horns and to characterize the evolutionary radiation of horns. Although our limited sampling of one of the world's most species-rich genera almost certainly underestimates the number of evolutionary events, our phylogeny reveals prolific evolutionary lability of these exaggerated sexually selected weapons (more than 25 separate gains and losses of five different horn types). We discuss these results in the context of the natural history of these beetles and explore ways that sexual selection and ecology may have interacted to generate this extraordinary diversity of weapon morphology.
ISSN:0014-3820
1558-5646
DOI:10.1554/04-642