Sunday, January 18, 2015

Good Genes and Sexual Selection in Dung Beetles

Onthophagus taurus male and female comparison.jpg
"Onthophagus taurus male and female comparison" by Source (WP:NFCC#4). Licensed under Fair use via Wikipedia.
Posted by Jessica Abbott for Jessica Åhlén-Sandblom 

This article by Garcia-Gonzalez and Simmons focus on the importance of the good genes model in female mate choice. 
One founding component of sexual selection is the existence of heritable variation in fitness. The good genes model tells us that this variance in quality is expressed phenotypically in the males and that females base their mate choice upon a trait that represent the male's good genes. 
The dung beetle has shown condition dependence of sexually selected traits and genetic correlations between preference and trait, thus comes the logical next step to see if the fitness of the father is inherited to the offspring.
Here they do a quantitative genetic analysis with a full-sib/half-sib design to compare the additive genetic effect of father on egg to adult and adult viability between families (one male mated with three females). 
They found a significant effect of the father for egg to adult viability and survival of sons but not daughters to adult age and no indication for sexual antagonism in genetic variation for fitness.
The authors argue for pre- and post-copulatory choice from females and competition between males to give the female indirect benefit in terms of higher offspring fitness in agreement with the good genes model.

Although this is not my current topic of research, I decided to share this article with you for three reasons. 
First of all, I have the possibility to do a similar project with Leigh Simmons (one of the authors) as my supervisor in the future, second because it relates with my ongoing project since they investigate paternally inherited fitness in a quantitative genetic study with a full-sib/half-sib breeding design and also discuss sexual antagonism briefly. And last, because it is short and neat (only 4 pages).

See you on Tuesday!
Jessica Åhlén Sandblom

Abstract: Whether species exhibit significant heritable variation in fitness is central for sexual selection. According to good genes models there must be genetic variation in males leading to variation in offspring fitness if females are to obtain genetic benefits from exercising mate preferences, or by mating multiply. However, sexual selection based on genetic benefits is controversial, and there is limited unambiguous support for the notion that choosy or polyandrous females can increase the chances of producing offspring with high viability. Here we examine the levels of additive genetic variance in two fitness components in the dung beetle Onthophagus taurus. We found significant sire effects on egg-to-adult viability and on son, but not daughter, survival to sexual maturity, as well as moderate coefficients of additive variance in these traits. Moreover, we do not find evidence for sexual antagonism influencing genetic variation for fitness. Our results are consistent with good genes sexual selection, and suggest that both pre- and postcopulatory mate choice, and male competition could provide indirect benefits to females.

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