Towards a resolution of the lek paradox

Genetic benefits in the shape of 'good genes' have been invoked to explain costly female choice in the absence of direct fitness benefits. Little genetic variance in fitness traits is expected, however, because directional selection tends to drive beneficial alleles to fixation. There seems to be little potential, therefore, for female choice to result in genetic benefits, giving rise to the 'lek paradox'. Nevertheless, evidence shows that genetic variance persists despite directional selection and genetic benefits of female choice are frequently reported. A theoretical solution to the lek paradox has been proposed on the basis of two assumptions: that traits are condition-dependent, and th…

Matters of scale: positive allometry and the evolution of male dimorphisms

J.L.T. was funded by a Biotechnology and Biological Sciences Research Council research fellowship, J.S.K. by the Academy of Finland, and N.R.L. by a Natural Environment Research Council research fellowship. The developmental independence of alternative phenotypes is key to evolutionary theories of phenotypic plasticity and the origins of diversity. Male dimorphisms associated with alternative reproductive tactics are widely cited examples of such facultative expression of divergent fitness optima. Current models for the evolution of male dimorphisms invoke a size-dependent threshold at which the phenotype is reprogrammed. We use predictions derived from allometric modeling to test for the e…

Males influence maternal effects that promote sexual selection: a quantitative genetic experiment with dung beetles Onthophagus taurus

J.S.K. was funded by the Academy of Finland, L.W.S. by the Australian Research Council, J.H. by an Australian Postgraduate Award, and J.L.T. by a postdoctoral research fellowship from the University of Western Australia. Recently, doubt has been cast on studies supporting good genes sexual selection by the suggestion that observed genetic benefits for offspring may be confounded by differential maternal allocation. In traditional analyses, observed genetic sire effects on offspring phenotype may result from females allocating more resources to the offspring of attractive males. However, maternal effects such as differential allocation may represent a mechanism promoting genetic sire effects…

The discrimination of alternative male morphologies

Male dimorphisms represent alternative selective regimes within a sex. As such, they can be used as a powerful tool in testing evolutionary theory. However, to realize this potential, we need to be able to accurately discriminate individuals into two separate morphs. In this article we discuss the existing methods and propose a new one. We test our method with data from three dimorphic species and compare these results to results with existing methods. We conclude that existing methods often misclassify a large proportion of individuals, but applying our method notably reduces these errors.

Genic capture and resolving the lek paradox

The genic capture hypothesis offers a resolution to the question of how genetic variation in male sexually selected traits is maintained in the face of strong female preferences. The hypothesis is that male display traits are costly to produce and hence depend upon overall condition, which itself is dependent upon genes at many loci. Few attempts have been made to test the assumptions and predictions of the genic capture hypothesis rigorously and, in particular, little attention has been paid to determining the genetic basis of condition. Such tests are crucial to our understanding of the maintenance of genetic variation and in the evaluation of recent models that propose a role for sexual …

On the resolution of the lek paradox.

Directional female mate choice is expected to deplete additive genetic variation in male traits. This should preclude such trait-based choice from resulting in genetic benefits to offspring, and yet genetic benefits are the explanation for the choice. This evolutionary conundrum is known as the lek paradox. Newly proposed resolutions to this paradox aim to unravel mechanisms that contribute to the persistence of genetic variance in traits under directional female mate choice.

Major Differences in Minor Allometries: A Reply to Moczek.

Abstract: By comparing alternative measurements of horn length in the beetle Onthophagus taurus, we have investigated why scaling patterns differ between laboratories. We show that some measurements are confounded by including part of the head in the horn size measurement and consistently underestimate the allometry of horns in minor males. Our data show how linear measures that avoid confounding horn length with head size produce scaling patterns that support a positive allometry rather than a reprogramming model of horn growth. We also found horn volume was highly positively allometric this estimate of growth therefore further supports a positive allometry model.

Intralocus tactical conflict: Genetic correlations between fighters and sneakers of the dung beetle Onthophagus taurus

Males and females differ in their phenotypic optima for many traits, and as the majority of genes are expressed in both sexes, some alleles can be beneficial to one sex but harmful to the other (intralocus sexual conflict; ISC). ISC theory has recently been extended to intrasexual dimorphisms, where certain alleles may have opposite effects on the fitness of males of different morphs that employ alternative reproductive tactics (intralocus tactical conflict; ITC). Here, we use a half-sib breeding design to investigate the genetic basis for ISC and ITC in the dung beetle Onthophagus taurus. We found positive heritabilities and intersexual genetic correlations for almost all traits investigat…

COMPARING EVOLVABILITIES: COMMON ERRORS SURROUNDING THE CALCULATION AND USE OF COEFFICIENTS OF ADDITIVE GENETIC VARIATION

In 1992, David Houle showed that measures of additive genetic variation standardized by the trait mean, CVA (the coefficient of additive genetic variation) and its square (IA), are suitable measures of evolvability. CVA has been used widely to compare patterns of genetic variation. However, the use of CVAs for comparative purposes relies critically on the correct calculation of this parameter. We reviewed a sample of quantitative genetic studies, focusing on sire models, and found that 45% of studies use incorrect methods for calculating CVA and that practices that render these coefficients meaningless are frequent. This may have important consequences for conclusions drawn from comparative…

On female choice, heterozygosity and the lek paradox

Data from: Intralocus tactical conflict: genetic correlations between fighters and sneakers of the dung beetle Onthophagus taurus

Males and females differ in their phenotypic optima for many traits, and since the majority of genes are expressed in both sexes, some alleles can be beneficial to one sex but harmful to the other (intralocus sexual conflict; ISC). ISC theory has recently been extended to intrasexual dimorphisms, where certain alleles may have opposite effects on the fitness of males of different morphs that employ alternative reproductive tactics (intralocus tactical conflict; ITC). Here we use a half-sib breeding design to investigate the genetic basis for ISC and ITC in the dung beetle Onthophagus taurus. We found positive heritabilities and intersexual genetic correlations for almost all traits investig…