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Sex and the Single Guppy

Intro | Discovery | Hypotheses | Simulation 1 | Analysis 1 | Simulation 2 | Analysis 2 | Conclusion | Gallery

Conclusion: Exhibitionism Explained

We've seen in our simulations that the more brightly colored a male guppy is, the more likely he will be seen -- and eaten -- by a predator. In a simulation or in the wild, where predators are plentiful, male guppies become increasingly drab over generations, pushed by predation pressure toward greater camouflage.

So if camouflage confers such an obvious survival benefit to prey species like guppies when it comes to predator avoidance, what possible advantage could there be to sporting colors and patterns that make an individual more conspicuous?

The answer lies in the fact that guppies have to do more than just survive. They also have to reproduce -- and to do that, they have to attract mates. The "flashier" a male guppy is, the more likely a female guppy will choose him as a mate, giving him the opportunity to pass his genes along to the next generation. This is sexual selection at work, and it is the force that pushes guppy coloration toward conspicuousness just as hard as predation pushes coloration toward drabness.

There may be several evolutionary reasons why female guppies prefer flashy males. On the most basic level, the male with the biggest, brightest tail spot announces most loudly, "Hey, I'm over here" to any female within eyeshot. Flashy colors are simply easier to locate.

Bright colors may also indicate good genes, in the way the strong physique of a human athlete is a direct indicator of that individual's health and vitality. And more indirectly, bright coloration may signal to a potential mate that he's got something else going for him. After all, he's been able to survive the very handicap -- conspicuousness to predators -- that his flashiness creates.

Whatever the reasons, it is clear from the research of Endler and other evolutionary biologists that male guppies live in the crossfire between their enemies and their would-be mates, with the opposing forces of predation and sexual selection forever pushing the guppy coloration in opposite directions.

-> Go to the Guppy Gallery

Intro | Discovery | Hypotheses | Simulation 1 | Analysis 1 | Simulation 2 | Analysis 2 | Conclusion | Gallery

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