Scheffers, Brett R., Whiting, Arthur V., and Paszkowski, Cynthia A. (2012) The roles of spatial configuration and scale in explaining animal distributions in disturbed landscapes: a case study using pond-breeding anurans. Raffles Bulletin of Zoology: Supplement Series, 25. pp. 101-110.

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Abstract

Scale is fundamental to ecological studies as patterns exist at multiple levels of organisation. Scale is critically important when assessing a species' distribution, and it can influence the results of complex landscape analyses. If ignored, conservation and management decisions may be inappropriate. In this study, we assessed an often overlooked element in landscape analyses, spatial configuration, to uncover patterns of species distribution. Specifically, we evaluated cover by native vegetation within an urban landscape using a non-nested approach based on discrete consecutive rings (e.g., 0-50 m, 50-100 m, etc.) and a traditional nested approach based on concentric circles (e.g., 0-50 m, 0-100 m, etc.) to determine whether these approaches differ in their effectiveness in uncovering relationships between land cover and animal occurrence in a disturbed, urban landscape. We performed spatial configuration analyses using two anuran amphibian species (wood frog, Lithobates sylvaticus; and boreal chorus frog, Pseudacris maculate) sampled via call surveys at 75 wetlands (of constructed stormwater sites [n=58] and natural wetlands [n=17]) located within the city of Edmonton, Alberta, Canada. Furthermore, we evaluated the relationship between proportion of native vegetation and species occurrence at three grain sizes (10 m, 50 m, and 100 m) based on analyses of non-nested concentric zones. The nested and non-nested approaches differed in their predictions regarding the occurrence of the frog species. The nested approach explained a higher percentage of deviance when predicting wood frog occurrence than did the non-nested analyses whereas the non-nested approach explained a higher percentage of deviance when predicting boreal chorus frog occurrence. We identified locations surrounding wetlands that predicted occurrence using the non-nested approach that were not detected by the nested approach, suggesting that non-nested analyses may represent an overlooked tool for habitat assessment. Top models for predicting occurrence varied among the three grain sizes, suggesting that our ability to detect environmental heterogeneity is scale-dependent. Incorporating spatial configuration (non-nested and nested designs) and multiple grain sizes in analyses may provide better resolution of landscape patterns and help uncover causes behind species' distributions.

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