Extinction, colonization, and species occupancy in tidepool fishes

  • Pfister C
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Abstract Despite the increasing sophistication of eco- logical models with respect to the size and spatial ar- rangement of habitat, there is relatively little empirical documentation of how species dynamics change as a function of habitat size and the fraction of habitat oc- cupied. In an assemblage of tidepool ®shes, I used maximum-likelihood estimation to test whether models which included habitat size provided a better ®t to em- pirical data on extinction and colonization probabilities than models that assumed constant probabilities over all habitats. I found species di����erences 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 Mac- Arthur-Wilson island-mainland model. When I incor- porated declines in extinction probability with tidepool volume in a simple simulation model, I found that pre- dicted 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 funda- mental to understanding how species are distributed spatially and whether metapopulation models of species occupancy provide explanatory power for ®eld popula- tions. Key words Habitat patches á Incidence functions á Insular habitats á Sculpins á Metapopulations Introduction

Author-supplied keywords

  • Habitat patches
  • Incidence functions
  • Insular habitats
  • Metapopulations
  • Sculpins

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  • Catherine A. Pfister

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