Extinction, colonization, and species occupancy in tidepool fishes |
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Authors: | Catherine A Pfister |
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Institution: | (1) Department of Zoology, NJ-15, University of Washington, Seattle, WA 98195, USA, US |
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Abstract: | Despite the increasing sophistication of ecological models with respect to the size and spatial arrangement of habitat, there
is relatively little empirical documentation of how species dynamics change as a function of habitat size and the fraction
of habitat occupied. In an assemblage of tidepool fishes, I used maximum-likelihood estimation to test whether models which
included habitat size provided a better fit to empirical data on extinction and colonization probabilities than models that
assumed constant probabilities over all habitats. I found species differences in how extinction and colonization probabilities
scaled with habitat size (and hence local population size). However, there was little evidence for a relationship between
extinction and colonization probabilities and the fraction of occupied tidepools, as assumed in simple metapopulation models.
Instead, colonization and extinction were independent of the fraction of occupied tidepools, favoring a MacArthur-Wilson island-mainland
model. When I incorporated declines in extinction probability with tidepool volume in a simple simulation model, I found that
predicted occupancy could change greatly, especially when colonization was low. However, the predicted fraction of occupied
patches in the simulation model changed little when I incorporated the range of values reported here for extinction and colonization
and the rate at which they scale with habitat size. Quantifying extinction and colonization patterns of natural populations
is fundamental to understanding how species are distributed spatially and whether metapopulation models of species occupancy
provide explanatory power for field populations.
Received: 14 March 1997 / Accepted: 21 September 1997 |
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Keywords: | Habitat patches Incidence functions Insular habitats Sculpins Metapopulations |
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