Population dynamics of shrews on small islands accord with the equilibrium model
作者:
Ilkka Hanski,
期刊:
Biological Journal of the Linnean Society
(WILEY Available online 1986)
卷期:
Volume 28,
issue 1‐2
页码: 23-36
ISSN:0024-4066
年代: 1986
DOI:10.1111/j.1095-8312.1986.tb01747.x
出版商: Blackwell Publishing Ltd
关键词: Sorex;island biogeography;extinction;demographic stochasticity;environmental stochasticity;competition;colonization;epigenetic variation
数据来源: WILEY
摘要:
Three of the six species of shrew in Finland,Sorex araneus, S. caecutiens, and S. minutus, are common on the mainland and widespread on islands in lakes. The islands range from 0.01 to 500 ha in area, and from 10 to 3000 m in isolation (distance from the mainland). The species‐area relationship, the lack of importance of habitat diversity, the increasing frequency of unoccupied small islands with isolation, and direct observations of small populations, all suggest that populations on small islands have a high extinction rate. Demographic stochasticity is the main cause of extinctions in the superior competitor,S. araneus, which occurs consistently on islands greater than 2 ha. The small species,S. caecutiens and S. minutus, are more sensitive to environmental stochasticity than isS. araneus, and are inferior to it in interspecific competition; these factors probably contribute to the absence of the small species from many islands tens of hectares in area. Frequent colonization of islands less than 500 m from the mainland is indicated by large numbers of shrews trapped from tiny islets where breeding is not possible, by increasing epigenetic divergence of island populations with isolation, and by observations of dispersal to and colonization of islands. Dispersal ability decreases with decreasing individual size, which may partly explain the absence of the small shrews from many relatively large islands. The shrew populations persist in a dynamic equilibrium on the islands. Epigenetic morphological variation is a useful tool in ecological studies of island population
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