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Trait-mediated indirect effects and complex life-cycles in two European frogs.


Altwegg, R (2002). Trait-mediated indirect effects and complex life-cycles in two European frogs. Evolutionary Ecology Research, 4:519-536.

Abstract

Most animals actively avoid predators. If such a reaction reduces competitive ability, for example by reducing food intake, predator presence can lead to trait-mediated indirect effects. Because predator avoidance typically leads to reduced growth rather than reduced survival, its
effect on population processes is difficult to assess. This is especially true for organisms with complex life-cycles, where predator avoidance during one stage is expected to lead to traitmediated indirect effects if it has effects reaching into the following life stages. I experimentally
investigated the effect of caged (thus non-lethal) dragonfly larvae on the competition between
tadpoles of two frog species (Rana lessonae and R. esculenta) and on juvenile frog survival during the subsequent terrestrial stage. In response to caged predators, R. lessonae delayed metamorphosis more than R. esculenta, but they both metamorphosed heavier. These
differences suggest the possibility of a competitive disadvantage for R. lessonae in the presence of predators, which could lead to trait-mediated indirect effects. However, the presence of predators did not modify competitive effects and had no measurable consequences on terrestrial survival. Regardless of the presence of predators, competition during the larval stage had large effects on metamorphosis and led to strongly decreased survival in the subsequent terrestrial stage. These results suggest that trait-mediated indirect effects are not important in this system, because the predator reaction of the tadpoles in both species had no measurable effect on the following life stage and, therefore, probably no strong effect on community dynamics.

Most animals actively avoid predators. If such a reaction reduces competitive ability, for example by reducing food intake, predator presence can lead to trait-mediated indirect effects. Because predator avoidance typically leads to reduced growth rather than reduced survival, its
effect on population processes is difficult to assess. This is especially true for organisms with complex life-cycles, where predator avoidance during one stage is expected to lead to traitmediated indirect effects if it has effects reaching into the following life stages. I experimentally
investigated the effect of caged (thus non-lethal) dragonfly larvae on the competition between
tadpoles of two frog species (Rana lessonae and R. esculenta) and on juvenile frog survival during the subsequent terrestrial stage. In response to caged predators, R. lessonae delayed metamorphosis more than R. esculenta, but they both metamorphosed heavier. These
differences suggest the possibility of a competitive disadvantage for R. lessonae in the presence of predators, which could lead to trait-mediated indirect effects. However, the presence of predators did not modify competitive effects and had no measurable consequences on terrestrial survival. Regardless of the presence of predators, competition during the larval stage had large effects on metamorphosis and led to strongly decreased survival in the subsequent terrestrial stage. These results suggest that trait-mediated indirect effects are not important in this system, because the predator reaction of the tadpoles in both species had no measurable effect on the following life stage and, therefore, probably no strong effect on community dynamics.

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24 citations in Web of Science®
23 citations in Scopus®
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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Zoology (former)
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Language:English
Date:2002
Deposited On:11 Feb 2008 12:15
Last Modified:05 Apr 2016 12:14
Publisher:Evolutionary Ecology Ltd
ISSN:1522-0613
Related URLs:http://www.evolutionary-ecology.com/issues/v04n04/eear1348.pdf
Permanent URL: http://doi.org/10.5167/uzh-503

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