Can kangaroo rat graminivory contribute to the persistence of desertified shrublands? |
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| Authors: | GIH Kerley WG Whitford |
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| Institution: | 1. Amarula Elephant Research Programme, School of Life Sciences, University of KwaZulu-Natal, Westville Campus, Private Bag X54001, Durban 4000, South Africa;2. Conservation Ecology Group, Groningen Institute for Evolutionary Life Sciences, University of Groningen, P.O. Box 11103, 9700 CC Groningen, The Netherlands;3. Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa;4. Department of Global Ecology, Carnegie Institution for Science, 260 Panama Street, Stanford, CA 94305, USA;5. Soil Biodiversity Group, Life Sciences Department, The Natural History Museum, London SW7 5BD, UK;6. Department of Genetics, Environment and Evolution, University College London, London WC1E 6BT, UK |
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| Abstract: | Medium-sized kangaroo rats (Dipodomys spp. Gray) function as keystone species in the dynamics of desert bunchgrasses. We tested the hypothesis that kangaroo rat graminivory leads to reduced grass growth and inflorescence production, and that kangaroo rat grass consumption reflects their preferences for open microhabitats. We excluded kangaroo rats from grasses, and measured tiller loss, leaf and tiller growth and inflorescence production. We recorded the extent of tiller loss in grasses varying in tussock size or the extent of surrounding cover. Consumption of tillers by kangaroo rats was extensive, peaking in late summer. Grasses protected from kangaroo rat graminivory showed elevated leaf and tiller growth and inflorescence production. Grass tussocks protected by surrounding vegetation or large grass tussocks suffered lower graminivory than tussocks in the open or small tussocks. Our data demonstrate that the mechanism of the keystone role of kangaroo rats is through direct graminivory. We hypothesize that kangaroo rat graminivory may contribute to the persistence of desertified shrublands by limiting grass recruitment and abundance. Medium-sized kangaroo rats prefer open microhabitats and increase in abundance as such microhabitats increase, suggesting a positive feedback, with kangaroo rats increasing in abundance in overgrazed, desertified landscapes, and then contributing to their persistence through graminivory. |
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