Evol Ecol Res 9: 299-311 (2007)     Full PDF if your library subscribes.

A field test of the centrifugal community organization model using psammophilic gerbils in Israel’s southern coastal plain

Gideon Wasserberg,1* Burt P. Kotler,2 Douglas W. Morris3 and Zvika Abramsky4

1USGS Wisconsin Cooperative Wildlife Research Unit, Department of Wildlife Ecology, University of Wisconsin, Madison, WI, USA,  2Mitrani Department of Desert Ecology, Jacob Blaustein Institute for Desert Research, Ben-Gurion University of the Negev, Midreshet Ben-Gurion, Israel,  3Department of Biology, Lakehead University, Thunder Bay, Ontario, Canada and  4Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel

Address all correspondence to G. Wasserberg, Department of Wildlife Ecology, University of Wisconsin, 207 Russell Laboratory, 1630 Linden Drive, Madison, WI 53706, USA.
e-mail: wasserberg@wisc.edu


Background: An optimal habitat selection model called centrifugal community organization (CCO) predicts that species, although they have the same primary habitat, may co-exist owing to their ability to use different secondary habitats.

Goal: Test the predictions of CCO with field experiments.

Species: The Egyptian sand gerbil (40 g), Gerbillus pyramidum, and Allenby’s gerbil (25 g), G. andersoni allenbyi.

Site: Ashdod sand dunes in the southern coastal plain of Israel. Three sandy habitats are present: shifting, semi-stabilized, and stabilized sand. Gerbils occupied all three habitats.

Methods: We surveyed rodent abundance, activity levels, and foraging behaviour while experimentally removing G. pyramidum.

Results: Three predictions of the CCO model were supported. Both species did best in the semi-stabilized habitat. However, they differed in their secondary habitats. Gerbillus pyramidum preferred the shifting sand habitat, whereas G. a. allenbyi preferred the stabilized habitat. Habitat selection by both species depended on density. However, in contrast to CCO, G. pyramidum dominated the core habitat and excluded G. a. allenbyi. We term this variant of CCO, ‘asymmetric CCO’.

Conclusions: The fundamental feature of CCO appears valid: co-existence may result not because of what each competing species does best, but because of what they do as a back-up. But in contrast to the prediction of the original CCO model, all dynamic traces of interaction can vanish if the system includes interference competition.

Keywords: asymmetric centrifugal community organization, Gerbillus andersoni allenbyi, Gerbillus pyramidum, giving-up density, habitat selection, mechanism of co-existence.

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        © 2007 Gideon Wasserberg. 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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