Evol Ecol Res 8: 1301-1309 (2006)     Full PDF if your library subscribes.

A trophic polymorphism induced by both predators and prey

B.R. Schmidt,^1,2* N. Ramer¹‡ and J. Van Buskirk¹

¹Zoologisches Institut, Universität Zürich, Winterthurerstrasse 190, 8057 Zürich and ²KARCH, Passage Maximilien-de-Meuron 6, 2000 Neuchâtel, Switzerland

Address all correspondence to B.R. Schmidt, Zoologisches Institut, Universität Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
e-mail: bschmidt@zool.unizh.ch

ABSTRACT

Problem: We tested whether plasticity in head shape of newt larvae represents a predator-induced resource polymorphism that may allow newts to compensate for costs of defence.

Organism: Larvae of European Triturus newts exhibit defensive behaviour and morphology when in ponds with predators. Predator-induced newt larvae also have large heads, although head shape does not have a direct influence on vulnerability to predation.

Methods: We surveyed the morphology and diet of T. alpestris larvae in 17 natural ponds. A laboratory experiment was used to assess the effects of predators and food size on trophic morphology.

Results: In natural ponds, individuals with relatively large heads had large prey, and a larger volume of prey, in their guts. In the experiment, a large head was induced by both prey size and predator cues, acting additively.

Conclusion: Even though the large head offers no protection from predation, it is directly induced by predators and enables newts to consume more profitable prey.

Keywords: inducible defence, morphology, phenotypic plasticity, prey size, resource polymorphism, Triturus.

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        © 2006 B.R. Schmidt. All EER articles are copyrighted by their authors. All authors endorse, permit and license Evolutionary Ecology Ltd. to grant its subscribing institutions/libraries the copying privileges specified below without additional consideration or payment to them or to Evolutionary Ecology, Ltd. These endorsements, in writing, are on file in the office of Evolutionary Ecology, Ltd. Consult authors for permission to use any portion of their work in derivative works, compilations or to distribute their work in any commercial manner.

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