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Plant defences to no avail?: Responses of plants of varying edibility to food web manipulations in a low arctic scrubland
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. (Department of Forest Resource Management, Swedish University of Agricultural Sciences, Uppsala, Sweden)
Department of Biology, Section of Ecology, University of Turku, Turku, Finland. (Department of Natural Sciences, Finnmark University College, Alta, Norway)
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
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2009 (English)In: Evolutionary Ecology Research, ISSN 1522-0613, Vol. 11, 1189-1203 p.Article in journal (Refereed) Published
Abstract [en]

Background: According to the Green World Hypothesis of Hairston, Smith, and Slobodkin,all plants are edible for some herbivores. Hence, the copious abundance of plant biomass,typical for terrestrial ecosystems, depends on the collective regulatory action of predators on the herbivore guild. According to the counterarguments of Polis and Strong, the defensive traits of terrestrial plants attenuate terrestrial trophic cascades to species-specific trickles,so elimination of predators might lead to increased abundance of inedible plants but will not influence community-level plant biomass.

Question: Does the elimination of predators from a low arctic scrubland, with high-quality forage plants and poorly edible evergreen ericoids, lead to a reduction of community-level plant biomass or to an increased abundance of well-defended evergreen ericoids?

Methods: In 1991, we introduced grey-sided voles (Myodes rufocanus) to islands, initially harbouring dense scrubland vegetation, and established permanent plots there. In 2000, we transplanted vegetation blocks from a large three-trophic-level island with voles and predators,to two-trophic-level islands with introduced voles but without resident predators, and also to vole-free one-trophic-level islands, and back to the three-trophic-level island. Vole densities were monitored by semi-annual live trapping. Vegetation was monitored by the point-frequency method.

Results: In the absence of predators, vole densities increased 3.7-fold and the communitylevel plant biomass was decimated. The least palatable plant group, evergreen ericoids,suffered especially heavily, whereas palatable herbaceous plants increased in abundance. However, all three functional plant groups responded positively to the elimination of grey-sided voles.

Conclusions: Our results corroborate the Green World Hypothesis, indicating that in the absence of predators, plant defences do not prevent runaway consumption of the vegetation.

Place, publisher, year, edition, pages
Evolutionary ecology , 2009. Vol. 11, 1189-1203 p.
Keyword [en]
arctic, food web dynamics, herbivory, Myodes rufocanus, plant defences, tolerance, trade-offs
National Category
Earth and Related Environmental Sciences Ecology
URN: urn:nbn:se:umu:diva-30971OAI: diva2:289781
Available from: 2010-01-25 Created: 2010-01-25 Last updated: 2012-04-17Bibliographically approved

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Dahlgren, JonasOksanen, TarjaOlofsson, Johan
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