Evol Ecol Res 7: 733-741 (2005)     Full PDF if your library subscribes.

Predator complement determines the relative success of tadpoles of the Rana esculenta complex

Bradley R. Anholt,1,2* Sonja Negovetic,1,3 Claudia Rauter1,4 and Christian Som1,5

1Abteilung Oekologie, Zoologisches Institut, Universität Zürich, Zürich, Switzerland,  2Department of Biology, University of Victoria, Victoria, BC, Canada,  3Institut für Pharmakologie und Toxicologie, Universität Zürich, Zürich, Switzerland,  4Department of Biology, University of Nebraska at Omaha, Omaha, NE, USA and  5WWF Switzerland, Zürich, Switzerland

Address all correspondence to Bradley R. Anholt, Department of Biology, University of Victoria, Victoria, British Columbia V8W 3N5, Canada.
e-mail: banholt@uvic.ca


Question: Does the identity of the apex predator in a system predict the relative success of closely related amphibian larvae?

Organisms: Larvae of the hybridogenetic european frog, Rana kl. esculenta, and its sexual host, R. lessonae.

Site: Three ponds supporting predatory fish and four ponds without fish but containing large invertebrate and amphibian predators in northern Switzerland.

Background: Rana esculenta is a better competitor than R. lessonae in a wide range of conditions and is also a larger, more fecund frog than R. lessonae. Under most conditions, models predict competitive exclusion of R. lessonae followed by extinction of R. lessonae.

Methods: In the field, we measured the change in frequency of the two taxa from the larval stage to metamorphosis. In the laboratory, we measured the activity of the two taxa and measured their vulnerability to odonate predators.

Conclusions: In the presence of fish, the frequency of R. lessonae declined relative to R. esculenta from the larval stage to metamorphosis. In the absence of fish and presence of other predators, the opposite was true. Rana esculenta was more active than R. lessonae and more vulnerable to predation. The two taxa are adapted to different predator complexes and the hybridogenetic system is maintained by occasional dispersal between dissimilar water bodies.

Keywords: activity, co-existence, distribution, habitat segregation, hybridogenesis, predation, Rana esculenta complex, tadpoles.

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