@article {1819,
	title = {Confidence of paternity and paternal care: covariation revealed through the experimental manipulation of the mating system in the beetle Onthophagus taurus},
	journal = {Journal of Evolutionary Biology},
	volume = {15},
	year = {2002},
	pages = {784-795},
	abstract = {Theoretical models of paternal care predict that facultative reductions in male care may occur under certain conditions. One important parameter that has been shown to influence the outcome of these models is a male{\textquoteright}s confidence of paternity. In this study, we tested whether the amount of care provided by horned males in the dimorphic beetle, Onthophagus taurus, varied with his confidence of paternity. Male care results in an increased weight of dung provided in the brood masses produced by the pair. Using the sterile male technique we showed that a horned male{\textquoteright}s paternity declined with the number of sneak males in the population. The relationship was nonlinear, with paternity declining most rapidly between a frequency of one and three sneaks, and stabilizing thereafter at about 50\%. A horned male{\textquoteright}s paternity was directly related to the number of copulations with the female, relative to the number of copulations achieved by sneaks. Horned males were shown to reduce their care in relation to their declining paternity. Video analysis demonstrated that reductions in male care occurred through a combination of male desertion and a trade-off between caring and paternity assurance behaviours. The number of fights with sneak males was negatively related to the amount of care provided by a horned male. These results suggest that by gauging his expected paternity through the number of fights with sneaks, a horned male is able to assess his paternity and reduce his investment accordingly. Our data thus provide strong empirical support for the proposed link between paternity and paternal care. },
	keywords = {alternative mating tactics, confidence of paternity, Onthophagus taurus, paternal care},
	author = {Hunt, John and Simmons, Leigh W.}
}
@article {1820,
	title = {The genetics of maternal care: direct and indirect genetic effects on phenotype in the dung beetle Onthophagus taurus},
	journal = {Proceedings of the National Academy of Sciences},
	volume = {99},
	number = {10},
	year = {2002},
	month = {may 14},
	pages = {6828-6832},
	abstract = {While theoretical models of the evolution of parental care are based on the assumption of underlying genetic variance, surpris- ingly few quantitative genetic studies of this life-history trait exist. Estimation of the degree of genetic variance in parental care is important because it can be a significant source of maternal effects, which, if genetically based, represent indirect genetic effects. A major prediction of indirect genetic effect theory is that traits without heritable variation can evolve because of the heritable environmental variation that indirect genetic effects provide. In the dung beetle, Onthophagus taurus, females provide care to offspring by provisioning a brood mass. The size of the brood mass has pronounced effects on offspring phenotype. Using a half-sib breeding design we show that the weight of the brood mass females produce exhibits significant levels of additive genetic variance due to sires. However, variance caused by dams is con- siderably larger, demonstrating that maternal effects are also important. Body size exhibited low additive genetic variance. However, body size exerts a strong maternal influence on the weight of brood masses produced, accounting for 22\% of the nongenetic variance in offspring body size. Maternal body size also influenced the number of offspring produced but there was no genetic variance for this trait. Offspring body size and brood mass weight exhibited positive genetic and phenotypic correlations. We conclude that both indirect genetic effects, via maternal care, and nongenetic maternal effects, via female size, play important roles in the evolution of phenotype in this species. },
	author = {Hunt, John and Simmons, Leigh W.}
}
@article {2035,
	title = {Threshold evolution in exotic populations of a polyphenic beetle},
	journal = {Evolutionary Ecology Research},
	volume = {4},
	year = {2002},
	pages = {587-601},
	abstract = {Polyphenic development is thought to play an important role in the evolution of phenotypic diversity and morphological novelties, yet the evolution of polyphenisms has rarely been docu- mented in natural populations. Here we compare the morphologies of male dung beetles (Onthophagus ttaurus; Coleoptera: Scarabaeidae) from populations introduced to Australia and the eastern United States. Males in this species express two alternative morphologies in response to larval feeding conditions. Males encountering favourable conditions grow larger than a threshold body size and develop a pair of horns on their heads, whereas males that encounter poor conditions do not reach this threshold size and remain hornless. Australian and US populations did not differ in overall body size ranges, but exhibited significant differences in the location of the critical body size threshold that separates alternative male morphs. Australian males remained hornless at much larger body sizes than males in US populations, resulting in substantial and significant differences in the average body size{\textendash}horn length allometry between exotic populations, as well as significant differences in morph ratios. The phenotypic divergence observed between field populations was maintained in laboratory populations after two generations under identical environmental conditions, suggesting a genetic basis to allometric divergence in these populations. Divergence between exotic O. taurus populations was of a magnitude and kind typically observed between species. We use our results to examine potential causes of allometric divergence in onthophagine beetles, and discuss the evolutionary potential of threshold traits and polyphenic development in the origin of morphological and behavioural diversity.},
	keywords = {adaptive phenotypic plasticity, alternative tactics, developmental threshold, exotic species, horn polyphenism, Onthophagus, status-dependent selection, threshold evolution.},
	author = {Moczek, Armin P. and Hunt, John and Emlen, Douglas J. and Simmons, Leigh W.}
}
