Queen's University researchers have discovered that seeking out the most attractive mate may be unhealthy for any offspring.
Using a "virtual fruit fly dating game", Biology professor Adam Chippindale and graduate student Alison Pischedda have found that mating with a "fit" partner actually leads to dramatically lower rates of reproductive success in the next generation.
The research also raises questions about how masculine and feminine traits may be expressed through genes.
The findings, published in the November edition of PLoS Biology, suggest quite a twist on evolutionary thinking: On average, the lowest quality couple produced the best offspring while the highest quality pair produced the worst offspring.
The Queen's research team measured the inheritance of "fitness" (quality and number of offspring) using samples of low-and-high-fitness males and a separate set of low-and-high-fitness females to uncover what occurs as a result of sexual selection, the Darwinian process by which organisms compete for, and choose, their mates. In some traditional models, sexual selection is the search to provide offspring with 'good genes' to increase their reproductive success.
But Chippindale's group suspected that things were not so simple, at least in their flies. If sexually antagonistic genes, or genes that benefit one sex while harming the other, are prevalent then "...females who seek out high-fitness males will find that they produce high quality sons, but this will have detrimental effects on their daughters," says Dr. Chippindale, a Canada Research Chair in evolutionary genetics.
The researchers findings supports the notion that sexually antagonistic genes exert powerful effects and mostly inhabit the X chromosome, which only females pass onto sons. So when females choose successful mates they will see no benefits to sons and will only incur the cost of less-fit daughters, says Dr. Chippindale. "Sexually antagonistic genes, may be harmful or compromise fitness by reducing fertility of the opposite sex."
Dr. Chippindale suggests that this phenomenon may operate in far more organisms than the fruit fly. "If there are genes which have effects that feminize or masculinize each individual, then the expression of a wide variety of such genes will produce a continuum of gender. People wonder why there is so much gender identity diversity in the human populations -- this kind of mechanism may help us get a handle on that."
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