Modeling patch occupancy: Relative performance of ecologically scaled landscape indices
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In fragmented landscapes, the likelihood that a species occupies a particular habitat patch is thought to be a function of both patch area and patch isolation. Ecologically scaled landscape indices (ESLIs) combine a species’ ecological profile, i.e., area requirements and dispersal ability, with indices of patch area and connectivity. Since their introduction, ESLIs for area have been modified to incorporate patch quality. ESLIs for connectivity have been modified to incorporate niche breadth, which may influence a species’ ease in crossing the non-habitat matrix between patches. We evaluated the ability of 4 ESLIs, the original and modified indices of area and connectivity, to explain patterns in patch occupancy of 5 forest rodents. Occupancy of eastern gray squirrels (Sciurus carolinensis), North American red squirrels (Tamiasciurus hudsconicus), fox squirrels (Sciurus niger), white-footed mice (Peromyscus leucopus), and eastern chipmunks (Tamias striatus) was modeled at 471 sites in 35 landscapes sampled from the upper Wabash River basin in Indiana. Models containing ESLIs received support for gray squirrels, red squirrels, and chipmunks. Modified ESLIs were important in models for red squirrels. However, none of the models demonstrated high predictive ability. Incorporating habitat quality and using surrogate measures of dispersal can have important effects on model results. Additionally, different responses of species to area, isolation, and habitat quality suggest that generalizing patterns of metapopulation dynamics was not justified, even across closely related species.
KeywordsConnectivity Forest rodent Metapopulation Niche breadth Patch area
We are grateful to hundreds of private landowners who allowed access to their properties. Dozens of field technicians and crew chiefs collected data or digitized GIS layers. J. Crick, T. Preuss, L. Connolly, and N. Engbrecht coordinated field efforts, helped develop field protocols, and collected and managed data. J. Goheen provided data from tree squirrel mobility studies. M. Miller provided the script for ESLI calculation. P. Waser, T. Wiegand, and two anonymous reviewers provided useful comments on the manuscript. Our GIS data sources included the Center for Advanced Applications in GIS at Purdue University, National Land Cover Data, Indiana Unified Watershed Assessment, and the National Water Information System. Funding was provided by the John S. Wright Fund, Department of Forestry and Natural Resources, Purdue University, the U.S. Department of Education Graduate Assistance in Areas of National Need Award P200A030188, and the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No. 2000-04649.
- Akaike H (1973) Information theory as an extension of the maximum likelihood principle. In: Petrov BN, Csaki F (eds) Second international symposium on information theory. Akademiai Kiado, BudapestGoogle Scholar
- Burnham KP, Anderson DR (2002) Model selection and multi-model inference. Springer-Verlag, New YorkGoogle Scholar
- Cooch E, White G (2004) Program MARK: a gentle introduction. Available from http://www.phidot.org/software/mark/docs/book/
- Koprowski JL (1994) Sciurus niger. Mamm Species 479:1–9Google Scholar
- Kozakiewicz M (1993) Habitat isolation and ecological barriers—the effect on small mammal populations and communities. Acta Theriol (Warsz) 38:1–30Google Scholar
- MacKenzie DI, Nichols JD, Lachman GB et al (2002) Estimating site occupancy rates when detection probabilities are less than one. Ecology 83:2248–2255Google Scholar
- Mumford RE, Whitaker JO Jr (1982) Mammals of Indiana. Indiana University Press, BloomingtonGoogle Scholar
- Nupp TE (1997) Population dynamics and community structure of granivorous forest rodents in a fragmented landscape. Dissertation, Purdue UniversityGoogle Scholar
- Swihart RK, Slade NA (2004) Modeling interactions of private ownership and biological diversity: an architecture for landscapes with sharp edges. In: Swihart RK, Moore JE (eds) Conserving biodiversity in agricultural landscapes: model-based planning tools. Purdue University Press, West LafayetteGoogle Scholar
- Swihart RK, Verboom J (2004) Using ecologically scaled landscape indices to assess biodiversity consequences of land use-decisions. In: Swihart RK, Moore JE (eds) Conserving biodiversity in agricultural landscapes: model-based planning tools. Purdue University Press, West LafayetteGoogle Scholar