Choosey females should, “like physicians, unclothe the subject, weigh, listen, observe vital capacity, and take blood, urine and fecal samples.” – so said Hamilton and Zuk in 1982, when they first posited that mate choice enables females to select healthy, disease-resistant males, and produce disease-resistant offspring.
While I’m not sure that this is the approach I’ll be taking, it seems that female mice are working along those lines. And research published today in BMC Evolutionary Biology suggests that it’s with good reason.
The researchers, led by Dustin Penn, wanted to test whether the female’s choice of mate affected the health and disease-resistance of their offspring. They tested the preferences of female mice for certain males, but then the choice was taken out of the mice’s paws (so to speak). Males were assigned to the females, so that some were able to mate with their preferred males, while others had non-preferred males.
The results of the research certainly suggest that the females’ choice of partner is an important one, both for reproductive success and for the health of their offspring. Females that mated with their preferred male produced significantly larger litters than those that mated with a non-preferred male. What’s more, the offspring of the preferred males were better able to cope with infection (from Salmonella, a common mouse pathogen).
It seems, however, that the offspring from preferred males were no better at controlling pathogen loads than offspring sired by non-preferred males, indicating that the fitness benefits were due to tolerance to infection rather than immune resistance (the ability to control or eliminate pathogens).
“[I expected] that if there are indirect benefits from sexual selection, they would have been for improved immune resistance,” she explains.
Raveh hopes their findings will stimulate renewed interest in parasite-mediated sexual selection, along with the rapidly growing interest in tolerance to infection.
So what do the researchers think is behind their findings? Previous work by Penn and others has shown that ability to resist and survive Salmonella infection is influenced by MHC genes and other loci. However, he emphasizes that they still need to determine whether the fitness benefits they found in this latest research were due to genetic effects or maternal allocation, and that either mechanism will be interesting to explore in future studies.
BMC Evolutionary Biology is an open access, peer-reviewed journal that considers articles on all aspects of molecular and non-molecular evolution of all organisms, as well as phylogenetics and palaeontology.