Detecting environmental impacts on metapopulations of mound spring invertebrates - Assessing an incidence function model

We use a stochastic patch occupancy model of invertebrates in the Mound Spr ings ecosystem of South Australia to assess the ability of incidence functi on models to detect environmental impacts on metapopulations. We assume tha t the probability of colonisation decreases with increasing isolation and t he probability of extinction is constant across spring vents. We run the mo dels to quasi-equilibrium, and then impose an impact by increasing the loca l extinction probability. We sample the output at various times pre- and po stimpact, and examine the probability of detecting a significant change in population parameters. The incidence function model approach turns out to h ave little power to detect environmental impacts on metapopulations with sm all numbers of patches. (C) 2001 Elsevier Science Ltd. All rights reserved.