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Bank Vole [Clethrionomys glareolus (Schreber, 1780)] Propagules of Different Sizes and Island Colonization
Journal of Biogeography
Vol. 16, No. 2 (Mar., 1989), pp. 173-180
Published by: Wiley
Stable URL: http://www.jstor.org/stable/2845091
Page Count: 8
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Resulting from demosgraphic stochasticity, larger propagules (number of colonizers) are predicted to colonize islands with a higher degree of success. However, minimum number of individuals needed to establish a population, with a certain probability, is also dependent on demographic parameters, such as natality and mortality. This paper examines the effect of propagule size on colonization success, using two demographically different populations of the bank vole [Clethrionomys glareolus (Schreber, 1780)]. Bank voles from Northern and Southern Sweden were experimentally introduced on twenty islands each, in the Stockholm Archipelago. Propagules consisted of two, four, ten or twenty voles. A simulation model was used to predict extinction probabilities, based on demographic stochasticity. Southern voles had a natality to mortality ratio above unity, and larger propagules colonized more effectively than did smaller, as predicted. Northern voles, with a natality to mortality ratio below unity, were all predicted to go extinct, but time to extinction was predicted to be dependent on propagule size. This pattern was observed. The original simple colonization model proposed by MacArthur & Wilson was found to predict colonization success as accurately as the more complex simulation model.
Journal of Biogeography © 1989 Wiley