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Bet-hedging 'key to natural selection'
Humans aren't the only ones to hedge their bets, says one Canadian biologist, and understanding this may help explain how nature will respond to future climate change.

Associate Professor Andrew Simons of Carleton University in Ottawa argues 'bet-hedging' is a neglected evolutionary strategy used by living organisms in general, to cope with changing environments.

He details his argument in this week's Proceedings of the Royal Society B.

"It could be much more important than previously thought," says Simons, who has reviewed 100 papers reporting bet-hedging in a broad range of life including micro-organisms, plants, insects, birds and reptiles.

There are a number of evolutionary strategies that life uses to respond to changing environments, says Simons.

They may adapt their physiology or behaviour to maximise their chance of survival.

For example, water fleas have evolved to be capable of growing protective armour in response to chemical signals from fish predators.

Organisms also phase out undesirable traits - only those individuals that thrive in a new environment pass on their genes, and hence their traits, to future generations.

This strategy can lead to a generation of well-adapted specialists. But what happens when the environment fluctuates - sometimes wildly?
Managing risk

Simons says there is a third aspect of natural selection that we need to pay more attention to.

It's a way of managing risk called bet-hedging that humans themselves use when, say, diversifying stock market investments.

"Over the long term we know that environments are quite variable," says Simons.

"Bet-hedging allows you to survive despite those fluctuations... it reduces the chance all out failure."

This strategy allows for a diversity of genotypes that includes traits that may not be advantageous in the short term, but will ensure an organism survives in a particular extreme environment.

For example, insects can produce eggs, some of which hatch immediately and some of which hatch after one or two years, says Simons.

While this reduces the number of offspring they have in the short term, it is a way of hedging against the possibility of a bad season where none of the current generation gets to reproduce.

"In an unpredictable environment, one expects bet-hedging to evolve," says Simons.

Simons says it is important to find out how prevalent bet-hedging is in nature, and to make some generalisations as what kinds of organisms evolve it.

"It may be that weedy species might be bet-hedgers to a greater extent than other species that are specialised," says Simons. "It might explain susceptibility to extinction."
Lack of hard evidence

But despite extensive anecdotal evidence and a strong theoretical case for bet-hedging, Simons says the sceintific evidence for it is weak, with only 12 of the 100 papers he studied actually showing bet-hedging traits were adaptive.

He says this calls for researchers to pay more attention to it in the future.

"Environments are variable," says Simons. "So if we want to predict how organisms will fare under future environmental change we have to take into consideration the bet-hedging strategies."

Professor Ross Alford of James Cook University in Townsville, has worked on bet-hedging in tadpoles, and agrees with Simons' findings.

"Current research on how organisms will adapt to climate change overlook factors such as bet-hedging," he says.

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