A Hedging Strategy

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Science  02 Dec 2005:
Vol. 310, Issue 5753, pp. 1391
DOI: 10.1126/science.310.5753.1391a

Seed dormancy is a common adaptation in annual plants that live in highly seasonal or unpredictable habitats such as deserts. By delaying germination, plants can hope to escape conditions that are likely to be adverse for seedling growth. However, rather than germinating at once in response to a favorable cue such as rainfall, plants hedge their bets by varying the germination rates according to how reliably the cue predicts future conditions. In a study of annuals in the Negev desert, Tielböger and Valleriani show that germination rates are higher for the relatively few seeds produced during dry years than for the large numbers of seeds produced in wet years, regardless of the abiotic cue. It appears that the plants predict the likelihood of future survival according to the density of seeds: a measure of the likely intensity of competition among seedlings. The authors suggest that information about the density of neighbors may be encoded in the seeds via maternal effects from the parent plant. — AMS

Oikos 111, 235 (2005).

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