2006 ◽  
Vol 71 (4) ◽  
pp. 865-870 ◽  
Author(s):  
Andreas Nyman ◽  
Charlotta Kvarnemo ◽  
Ola Svensson

Genetics ◽  
1981 ◽  
Vol 97 (3-4) ◽  
pp. 719-730
Author(s):  
John G Brittnacher

ABSTRACT The genetic variation and genetic load due to virility, the male reproductive component of fitness, was measured in Drosophila melanogaster and D. pseudoobscura using males homozygous and heterozygous for the second chromosome of each species. Virility was determined in a female-choice, male mating competition experiment where both mating propensity and fertility were taken into account.——The mean virility of the homozygous D. melanogaster males relative to the heterozygous males was 0.50; the relative mean virility of the quasinormal homozygotes was 0.56. The mean virility of the homozygous D. pseudoobscura males relative to the heterozygous males was 0.70; the relative mean virility of the nonsterile homozygotes was 0.72, and of the quasinormal homozygotes, 0.68.——Depending on the species and chromosome sampled, fertile homozygous males had a mean virility 15 to 50% lower than the mean viability of individuals homozygous for a chromosome with quasinormal viability. The genetic load due to virility was also greater than that due to the female reproductive component. This higher level of hidden genetic variation (or genetic load) indicates that the results of PROUT(1971a, b) and BUNDGAARD and CHRISTIANSEN(1972), where the virility component of fitness dominated the dynamics of an artificial polymorphism, may be more general and that virility may dominate the dynamics of natural polymorphisms as well.


Author(s):  
Tracy Vaillancourt ◽  
Jaimie Arona Krems

Although the effects of sexual selection on male mating competition and intrasexual aggression have been studied extensively for well over a century, female mating competition and intrasexual aggression have only begun to receive serious attention in recent decades. Here, we focus on one aspect of sexually selected competition in girls and women—rival derogation, which takes the form of indirect aggression. We argue that this tactic of intrasexual competition both reduces a rival’s ability to compete for desirable mates and helps aggressors achieve and maintain their own high social status. We further argue that physical attractiveness initiates the pathway leading to high social status, which is preserved through the use of indirect aggression and is associated with increased dating and sexual behavior.


2011 ◽  
Vol 2 (1) ◽  
pp. 1-4 ◽  
Author(s):  
Daniel J Kruger ◽  
Stephen P Polanski

Male behavior and physiology is designed for enhanced competitiveness at the expense of longevity, resulting in higher mortality rates compared to females in most species. These differences vary across populations consistent with factors indicating the intensity of male mating competition. Reproductive dynamics are strongly influenced by the relative proportions of potentially reproductive males and females in a population. Because the reproductive strategies of men and women are somewhat divergent, market influences on the intensity of mating competition and selectivity for partners produce different outcomes in female biased and male biased populations. The single-child law implemented in China in 1979 has led to increasing proportions of men in the Chinese population. Using historical mortality data, we found a trend for increasing sex differences in Chinese mortality rates from 1982 to 2000. This increase was most prevalent in young adulthood, when male mating competition is most intense as males reach sexual maturity and seek female partners. In contrast, males exhibited more survival gains than females in infancy and early childhood.


Behaviour ◽  
2007 ◽  
Vol 144 (12) ◽  
pp. 1473-1495 ◽  
Author(s):  
Margaret Crofoot

AbstractI investigate the ecological context of intergroup agonism (IGA) in white-faced capuchins (Cebus capucinus) to elucidate the roles of feeding and mating competition, explicitly exploring both long- and short-term competitive strategies. Short-term mating competition is not a major function of IGA in C. capucinus. Males were the primary participants in IGA, but did not attempt to prevent extra-group copulations by herding females, and there was no relationship between IGA rate and conception rate. Long-term mating competition, on the other hand, may be important: 41% of interactions were low intensity, as would be expected if males were assessing the composition of neighboring groups in anticipation of a takeover. However, 59% of intergroup interactions escalated to chases or physical contact and females were frequent participants in IGA, directing aggression at adults of both sexes and at juveniles. These findings are not consistent with male mating competition and, in conjunction with overlapping home ranges, high interaction rate, and a positive relationship between IGA rate and both food availability and fruit patch size, they indicate that intergroup feeding competition may be important for capuchins. However, interactions do not preferentially occur at food sources, suggesting that capuchins may gain long-term, rather than short-term, benefits from IGA.


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