Lab-meeting: negative frequency-dependent selection and a rock-paper-scissor game going on in Drosophila melanogaster?

Posted by Erik Svensson

Inspired by the recent media buss of our sexual selection study on Drosophila melanogaster, which got nice coverage in major media such as New York Times and Washington Post, I would like to dedicate the next lab-meeting other fascinating aspects of fruit flies and sexual selection. It is amazing that so much still remains to be known about this well-studied animal, isn't it?

This time we will discuss an interesting question: is there evidence of a rock-paper-scissor game in D. melanogaster, and if so does it maintain genetic variation?

The article we will discuss was published in Molecular Ecology, and you can find it here. There is also a nice and a brief commenting article by Adam Chippindale in the same issue, which you can find here.

For those of you who do not know what the rock-paper-scissor game is, it is a special form of negative frequency-dependent selection, where each genotype (or morph) has its own strength and weakness, and all morphs co-exist over evolutionary time, due to a particular fitness pay off structure. The first empirical example of a rock-paper-scissor game that was described was for the colour polymorphic side-blotched lizard (Uta stansburiana) in California, by Barry Sinervo. For years, many have thought this system was unique and perhaps not very representative, but the new fruit fly study might suggest otherwise.

 I hope you will enjoy these articles and the discussion. Abstract is found below. Time and place as usual:

When: Tuesday, November 11, at 10.30
Where: "Argumentet", 2nd floor, Ecology Building.

Welcome!

Natural genetic variation in male reproductive genes contributes to nontransitivity of sperm competitive ability in Drosophila melanogaster

1. Rui Zhang,
2. Andrew G. Clark and
3. Anthony C. Fiumera

Abstract

Female Drosophila melanogaster frequently mate with multiple males, and the success of a given male depends not only on his genotype but also on the genotype of his competitor. Here, we assess how natural genetic variation affects male–male interactions for traits influencing pre- and postcopulatory sexual selection. Males from a set of 66 chromosome substitution lines were competed against each other in a ‘round-robin’ design, and paternity was scored using bulk genotyping. We observed significant effects of the genotype of the first male to mate, the second male to mate and an interaction between the males for measures of male mating rate and sperm utilization. We also identified specific combinations of males who show nontransitive patterns of reproductive success and engage in ‘rock-paper-scissors’ games. We then tested for associations between 245 polymorphisms in 32 candidate male reproductive genes and male reproductive success. We identified eight polymorphisms in six reproductive genes that associate with male reproductive success independent of the competitor (experimentwise P < 0.05). We also identified four SNPs in four different genes where the relative reproductive success of the alternative alleles changes depending on the competing males' genetic background (experimentwise P < 0.05); two of these associations include premature stop codons. This may be the first study that identifies the genes contributing to nontransitivity among males and further highlights that ‘rock-paper-scissors’ games could be an important evolutionary force maintaining genetic variation in natural populations.