@article {1562,
	title = {Diet alters male horn allometry in the beetle Onthophagus acuminatus (Coleoptera: Scarabaeidae)},
	journal = {Proceedings of the Royal society of London B},
	volume = {264},
	year = {1997},
	pages = {567-574},
	abstract = {Darwin considered the horns of male beetles to be among the most striking examples of sexual selection. As with antlers in deer or elk, beetle horns scale positively with male body size, with the result that large males have disproportionately longer horns than small males. It is generally assumed that such scaling relationships ({\textquoteleft} static allometries {\textquoteright}) are insensitive to short-term changes in the environment, and for this reason they are regularly used as diagnostic attributes of populations or species. Here I report breeding experiments on horned beetles that demonstrate that the scaling relationship between male horn length and body size changes when larval nutrition changes. Males reared on a low-quality diet had longer horn lengths at any given body size than sibling males reared on a high-quality diet. Such {\textquoteleft} allometry plasticity {\textquoteright} may explain seasonal changes observed in this same scaling relationship in a natural population. These experiments demonstrate that scaling relationships of sexually selected traits can respond facultatively to variation in the environment, thereby revealing a new mechanism by which males regulate the production of exaggerated secondary sexual traits. },
	author = {Emlen, Douglas J.}
}
@article {1791,
	title = {Genital morphology and fertilization success in the dung beetle Onthophagus taurus: an example of sexually selected male genitalia},
	journal = {Proceedings of the Royal society of London B},
	volume = {270},
	year = {2003},
	pages = {447-455},
	abstract = {In animals with internal fertilization and promiscuous mating, male genitalia show rapid and divergent evolution. Three hypotheses have been suggested to explain the evolutionary processes responsible for genital evolution: the lock-and-key hypothesis, the pleiotropy hypothesis and the sexual-selection hypoth- esis. Here, we determine whether variation in male genital morphology influences fertilization success in the dung beetle Onthophagus taurus, as predicted by the sexual-selection hypothesis. Variation in four out of five genital sclerites of the endophallus influenced a male{\textquoteright}s fertilization success, supporting the general hypothesis that male genitalia can evolve under sexual selection. Furthermore, different genital sclerites were found to enhance first versus second male paternity, indicating that different sclerites serve offensive and defensive roles. Genital-trait variability was comparable to that in other species but was less variable than a non-genital sexually selected trait (head horns). We suggest that directional selection for genital elaboration may be countered by natural selection, which should favour genitalia of a size and shape necessary for efficient coupling and sperm transfer. },
	keywords = {male genitalia, Onthophagus, paternity, sexual selection, Sperm competition},
	author = {House, Clarissa M. and Simmons, Leigh W.}
}
