Abstract
We sought to understand how the separation of habitats into spatially isolated fragments influences the abundance of organisms. Using a simple, deterministic model of population growth, we compared analytically exact solutions predicting abundance of consumers in two isolated patches with abundance of consumers in a single large patch where the carrying capacity of the large patch is the sum of the carrying capacities of the isolated ones. For the deterministic model, the effect of fragmentation was to slow the rate of population growth in the fragmented habitat relative to the intact one. We also analyzed a stochastic version of the model to examine the effect of fragmentation on population abundance when resources vary randomly in time. For the stochastic model, the effect of fragmentation was to reduce population abundance. We proved in closed-form, that for a non-equilibrium population exhibiting logistic population growth, fragmentation will reduce population size even when the total carrying capacity is not affected by fragmentation. We provide a theoretical basis for the prediction that habitat fragmentation amplifies the effect of habitat loss on the abundance of mobile organisms.
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Acknowledgements
Support for this work was provided by the National Science Foundation Grant: “Effects of Habitat Fragmentation on Consumer Resource Dynamics in Environments Varying in Space and Time”, Grant No. DEB0444711, and by NSF-IGERT Grant DGE-#0221595 administered by the PRIMES program at Colorado State University. We thank K. Searle and two anonymous reviewers for helpful comments on the manuscript. The work reported here was supported in part by the National Science Foundation while Hobbs was serving as a rotating Program Director in the Division of Environmental Biology. Any opinions, findings, conclusions, or recommendations are those of the authors and do not necessarily reflect the views of the National Science Foundation.
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Herbener, K.W., Tavener, S.J. & Hobbs, N.T. The distinct effects of habitat fragmentation on population size. Theor Ecol 5, 73–82 (2012). https://doi.org/10.1007/s12080-010-0097-6
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DOI: https://doi.org/10.1007/s12080-010-0097-6