@article {1565,
	title = {Phylogenetic evidence for an association between tunneling behavior and the evolution of horns in dung beetles (Coleoptera : Scarabaeidae : Scarabaeinae)},
	journal = {Coleopterists Bulletin},
	volume = {60},
	number = {5},
	year = {2006},
	note = {Times Cited: 0Suppl. S},
	month = {Dec},
	pages = {47-56},
	abstract = {Dung beetles employ numerous behavioral strategies to sequester dung away from other insects, and these have been broadly grouped into two categories: species that dig tunnels beneath the dung (tunnelers) and species that roll dung on the surface of the soil (rollers). Many species also are armed with rigid exoskeletal outgrowths called horns. Horns function as weapons, and horn sizes can be extreme. One widespread pattern within dung beetles is that tunneling species often have horns, whereas rolling species almost always do not, suggesting that residing (and fighting) inside tunnels at the dung deposition site may be an important ecological prerequisite for the evolution of horns in dung beetles. Here, we test explicitly for an historical association between tunneling behavior and the evolution of horns using a recent phylogeny for the scarabaeine dung beetles. We show that all eight of the independent gains of horns included in our analyses occurred on branches of the phylogeny reconstructed as tunneling, and that one of the three evolutionary losses of horns occurred on a branch that had lost tunneling behavior. We interpret this as evidence for a biologically meaningful association between tunneling behavior and the evolution of enlarged or exaggerated weapons such as horns, supporting the ideas of Eberhard and others that beetle horns may be most "beneficial" when used within the confines of restricted spaces such as burrows or tunnels.},
	keywords = {ALTERNATIVE REPRODUCTIVE TACTICS, body-size, DIMORPHISM, FEMALE CHOICE, FIDDLER-CRAB, FIGHTS, FOOD RELOCATION, onthophagus-taurus, SELECTION, SEXUAL, TRADE-OFFS},
	isbn = {0010-065X},
	url = {<Go to ISI>://000243611100005 },
	author = {Emlen, D. J.}
}
@article {1570,
	title = {Phylogenetic evidence for an association between tunneling behavior and the evolution of horns in dung beetles (Coleoptera : Scarabaeidae : Scarabaeinae)},
	journal = {The Coleopterists Bulletin},
	volume = {60},
	number = {5},
	year = {2006},
	note = {Times Cited: 0Suppl. S},
	month = {Dec},
	pages = {47-56},
	type = {monograph},
	abstract = {Dung beetles employ numerous behavioral strategies to sequester dung away from other insects, and these have been broadly grouped into two categories: species that dig tunnels beneath the dung (tunnelers) and species that roll dung on the surface of the soil (rollers). Many species also are armed with rigid exoskeletal outgrowths called horns. Horns function as weapons, and horn sizes can be extreme. One widespread pattern within dung beetles is that tunneling species often have horns, whereas rolling species almost always do not, suggesting that residing (and fighting) inside tunnels at the dung deposition site may be an important ecological prerequisite for the evolution of horns in dung beetles. Here, we test explicitly for an historical association between tunneling behavior and the evolution of horns using a recent phylogeny for the scarabaeine dung beetles. We show that all eight of the independent gains of horns included in our analyses occurred on branches of the phylogeny reconstructed as tunneling, and that one of the three evolutionary losses of horns occurred on a branch that had lost tunneling behavior. We interpret this as evidence for a biologically meaningful association between tunneling behavior and the evolution of enlarged or exaggerated weapons such as horns, supporting the ideas of Eberhard and others that beetle horns may be most "beneficial" when used within the confines of restricted spaces such as burrows or tunnels.},
	keywords = {ALTERNATIVE REPRODUCTIVE TACTICS, body-size, DIMORPHISM, FEMALE CHOICE, FIDDLER-CRAB, FIGHTS, FOOD RELOCATION, onthophagus-taurus, SELECTION, SEXUAL, TRADE-OFFS},
	isbn = {0010-065X},
	url = {<Go to ISI>://000243611100005 },
	author = {Emlen, Douglas J. and Philips, T. Keith}
}
@article {1899,
	title = {Horn size predicts physical performance in the beetle Euoniticellus intermedius (Coleoptera : Scarabaeidae)},
	journal = {Functional Ecology},
	volume = {19},
	number = {4},
	year = {2005},
	month = {Aug},
	pages = {632-639},
	abstract = {1. In many animals, the size of secondary sexual ornaments is known to be related to the probability of victory in fights between males, and hence to fighting ability. However, few studies have attempted to link fighting ability to any physical performance measures. 2. Here we show that horn size in the dung beetle Euoniticellus intermedius accurately predicts two types of whole-organism performance, independent of body size, that are likely to play an important role in male contests: the force required to pull a beetle out of a tunnel, and the distance the beetle was able to run before exhaustion (maximum exertion). 3. Body length is also a statistically significant predictor of pulling force, but not of exertion, suggesting that horn size is a more reliable predictor of performance than body size alone, a result that is consistent with a previous finding that horn size becomes more important in determining victory in male-male contests as body size increases. 4. This study is the first to establish direct links between whole-organism performance abilities, male armaments and fighting ability in the same species. Our findings suggest that physiological performance capacities are important factors underlying the evolution of signal expression in E. intermedius, and should be considered in future studies of the evolution of animal signalling.},
	keywords = {ALTERNATIVE REPRODUCTIVE TACTICS, anolis lizards, dimorphic male beetles, Dung beetles, energy-metabolism, hermit-crab fights, locomotor performance, male combat, onthophagus-acuminatus coleoptera, signalling, social-dominance, whole-organism performance},
	url = {<Go to ISI>://000231397300011 },
	author = {Lailvaux, S. P. and Hathway, J. and Pomfret, J. and Knell, R. J.}
}
@article {1966,
	title = {Horn possession reduces maneuverability in the horn-polyphenic beetle, Onthophagus nigriventris},
	journal = {Journal of Insect Science},
	volume = {6},
	number = {21},
	year = {2006},
	pages = {1-10},
	abstract = {Alternative male morphologies are common in a wide range of organisms and particularly extreme in horned beetles. Here, large males (majors) commonly develop extravagant weaponry such as horns or enlarged mandibles, whereas small males (minors) develop only rudimentary traits. In some taxa, including the genusOnthophagus, the transition from minors to majors occurs over a very small range of body sizes causing intermediate morphologies to be rare or absent from natural populations. Several studies have shown that majors use horns as weapons during male combat over females and that the possession of horns increases male fighting success, and presumably fitness. However, the advantages of a hornless morphology, if any, have remained elusive. Here the alternative male morphs are examined in the horn-polyphenic beetleOnthophagus nigriventris. In particular, the hypothesis was tested that lack of horns in minors increases their maneuverability inside tunnel systems in which these males sneak matings from major males. Using a simple behavioral assay the effects of horn possession on maneuverability were quantified inside an artificial tunnel. Minors were found to be significantly more mobile compared to majors. No such differences were found in mobility between similarly small and large females, which always lack horns. This suggests that mobility differences observed among male morphs are due to the presence or absence of horns rather than differences in body size. This notion was further supported in a second experiment in which surgical removal of horns significantly improved maneuverability, while subsequent re-attachment of horns reversed this effect. These results suggest that lack of horns increases male maneuverability inside tunnels and may thus be advantageous in the context of the particular social niche inhabited by minor males. The results are discussed in the context of the evolutionary ecology of horn-polyphenic beetles. },
	keywords = {ALTERNATIVE REPRODUCTIVE TACTICS, Horned beetle, phenotypic plasticity, Polyphenism, sexual selection},
	author = {Madewell, Richard and Moczek, Armin P.}
}
@article {2096,
	title = {Body size and paternal invest ment in the genus Onthophagus (Coleoptera, Scarabaeoidea)},
	journal = {Journal of Zoology},
	volume = {255},
	year = {2001},
	note = {EnglishArticleNOV3J ZOOL},
	pages = {405-412},
	abstract = {During reproduction, dung beetles of the genus Onthophagus typically bury portions of dung removed from the dung pad. Even though females are capable of successfully constructing and provisioning nests when unaccompanied by males, extensive levels of co-operation between sexes have been reported. In some species, males show a clear dimorphism in body plan and only large horned males are known to assist females. In O. taurus this form of paternal investment is facultative and depends on social context (namely the presence of other males). We studied relationships between body size and paternal investment in five Onthophagus species (i.e. O. coenobita, O. fracticornis, O. illyricus, O. taurus and O. vacca). Two types of tests were established. In test A, a large and a small male were placed with a single, medium-size female, in test B, a large and a small female were placed with a single large male. In controls one male was placed with one female. Individuals were maintained for 10 days. Then the enclosures were opened to assess the position of each beetle. When two mates were found in close vicinity or in the same tunnel provisioning dung, a co-operative behaviour was assumed. In competitive tests, small males and small females never cooperated with their potential mates whilst large and medium-size individuals often co- operated with mates inside the same tunnels. No differences in frequencies of co-operation were found between large and medium-size females. Small females and small males scarcely co- operated with large or medium-size mates in controls. These results suggest that large individuals outcompete the small ones. They also suggest that paternal investment depends on body size of both mates. Large males of all species assist medium-size and large females, whereas small males do not. However, large males do not invest much parental effort on small females that, in fact, are poorly, assisted. We assume that large individuals of both sexes are reproductively superior to small ones. The propensity of both small females and small males to excavate was lower than that of larger individuals, accordingly, digging capacity could be a proximate factor explaining facultative paternal investment in these species.},
	keywords = {ACUMINATUS COLEOPTERA, ALTERNATIVE REPRODUCTIVE TACTICS, beetle, body size, BROOD CARE, co-operation, Dung beetles, investment, MALE HORN DIMORPHISM, MALE MORPHOLOGY, Onthophagus, paternal, reproduction, Scarabaeidae, TAURUS COLEOPTERA, VACCA COLEOPTERA},
	author = {Palestrini, C. and Rolando, A.}
}
