Plasticity or fixed adaptive traits? Strategies for predation avoidance in Rana arvalis tadpoles |
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Authors: | Björn Lardner |
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Institution: | (1) Department of Animal Ecology, Ecology Building, S-223 62 Lund, Sweden e-mail: Bjorn.Lardner@zooekol.lu.se, Fax: +46-46-2224716, SE |
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Abstract: | Tadpoles of Rana arvalis originating from seven island populations were tested for responses to non-lethal predator presence. In general, tadpole
growth was reduced and the relative tail depth was increased at predator presence. There was no effect of predator presence
on the predicted size at metamorphosis. The differentiation rate, translating as length of the larval period, was lower at
predator presence, but this seems to be merely an effect of the reduced growth. Although populations differed with respect
to growth, relative tail length, relative tail depth, differentiation rate and predicted size at metamorphosis, no obvious
differences were found in their responses to predator presence. Data on predator occurrences in the source ponds show that
tadpoles originating from ponds with a high predation pressure have a higher differentiation rate, i.e. they will metamorphose
at an earlier date than those from “safe” ponds (if raised under the same conditions). Moreover, they are also predicted to
metamorphose at a smaller size, which is in accordance with theoretical models. Despite the fact that populations differed
in growth, no correlation was found between growth and predation risk in the source ponds.
Received: 16 March 1998 / Accepted: 18 July 1998 |
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Keywords: | Amphibians Predation Plasticity Adaptation Life history |
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