Posted by Alli (220.127.116.11) on February 13, 2002 at 15:04:22:
"Love is a battlefield: First direct evidence of sexual arms race."
14 February 2002
from "Nature" news
Both sexes have specialized hardware to help them get their way
Two hearts beating as one this Valentine's Day? Get real. "It's rarely the case that what's good for one sex is good for the other," says ecologist Locke Rowe. Rowe's research has revealed an eternal battle of the sexes in a water insect. He suspects it illustrates an arms race running across the animal kingdom.
Female water striders evolve to evade male attentions, and males evolve to overcome female resistance. Both sexes have specialized hardware to help them get their way. Male genitalia have powerful clasps, and females have spines on their abdomens that dislodge their suitors.
Researchers believe that natural selection hones ever-better weaponry. But they've had trouble catching evolution in the act. If both sexes are adapting, they can appear to be standing still.
To get round this, Rowe, who works at the University of Toronto, and his colleague Göran Arnqvist of the University of Uppsala, Sweden, looked at 15 closely related water- strider species. Comparing the amount of sex with each species' adaptations for getting or avoiding it revealed an even power balance in most species1.
If both sexes are adapting, they can appear to be standing still
The duo did find a few species where one sex had the upper hand - perhaps temporarily. "By looking at imbalances we can see the consequences of an arms race that is otherwise hidden," says Rowe.
The effort of mating, the risk of sexually transmitted disease and the greater chance of getting caught by a predator while in an embrace makes females keep contact to a minimum - just enough to fertilize their eggs.
For a male, every female is a potential vessel for carrying his genes into the next generation. Males provide no parental care, and benefit from mating with as many females as possible.
Arnqvist, G. & Rowe, L. Antagonistic coevolution between the sexes in a group of insects. Nature, 415, 787 - 789, (2002).
© Nature News Service / Macmillan Magazines Ltd 2002
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