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Is it really bet-hedging?

Before the ink is even dry on our Current Biology paper on bet-hedging in rhizobia (actually, before it's even printed), Xue-Xian Zhang and Paul B Rainey have critiqued it in Genome Biology. They summarize Will Ratcliff's results, then ask "whether it is an evolutionary response to fluctuating selection shaped by natural selection." Experimental evolution, an approach Rainey and colleagues have used successfully, would be a good way to answer this question.

But is it really even bet-hedging? To qualify as bet-hedging, you need to sacrifice arithmetic-average fitness to gain greater geometric-average fitness. That would obviously depend on the environment, but it seems reasonable to assume that having half your progeny go dormant would sacrifice fitness when food is abundant, while increasing the chances of having at least one surviving progeny under starvation.

Zhang and Rainey seem to think there's an additional requirement to qualify as bet-hedging, namely, "switching rates to suit prevailing conditions." I disagree. Isn't a 50:50 mix of stocks and bonds (rather than 100% stocks, which have higher average return but are riskier) considered bet-hedging, even if you never change that ratio? But I do agree that it's important to know whether the ratio of dormant to growing cells changes in response to conditions, which I would call phenotypic plasticity. We are working on that.

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