Saturday, April 3, 2010
Post Mating Competition
Coyne talks of post mating competition on page 151 where even after a male has mated with another female, other males may still try to mate with the inseminated female. Other males would first remove the sperm already inside the female reproductive tract and attempt to fertilize the female himself and steal his paternity. For example the Royal Entomological Society published an article where Drosophila melanogaster were able to "extensively displace previously stored sperm". If the females have spent so much time selecting a proper mate (we know they do because of sexual selection where males compete for females), why is it that the females have not developed a defense mechanism against such devious "weapons" --as Coyne likes to call them-- so that they may keep the revered semen of the mate they chose? Why even choose if all the ejaculate may just be stolen away by another probing male?
One answer I have is that the newer male that has the opportunity to remove semen from the genital tract and introduce his own, then the newer male must be more stronger and more fit to pass along its genes. But then does this not destroy the whole point of sexual selection if stronger and better males can just come along and steal another's paternity? How does post mating competition affect sexual selection overall? Would it be advantageous or disadvantageous for the species?
Why Evolution is True by Jerry Coyne
Ejaculate competition journal article: http://www3.interscience.wiley.com/journal/119862154/abstract?CRETRY=1&SRETRY=0