Predicting aquatic vertebrate assemblages from environmental variables at three multistate geographic extents of the western USA |
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| Affiliation: | 1. Amnis Opes Institute and Department of Fisheries & Wildlife, Oregon State University, 200 SW 35th Street, Corvallis, OR 97333, USA;2. Department of Fisheries & Wildlife, Oregon State University, 200 SW 35th Street, Corvallis, OR 97333, USA;3. Department of Statistics, Oregon State University, 44 Kidder Hall, Corvallis, OR 97331, USA;1. Department of Chemistry, Faculty of Natural Sciences, University of Elbasan, Elbasan, Albania;2. Department of Chemistry, Faculty of Natural Sciences, University of Tirana, Tirana, Albania;3. Department of Chemistry, University of Vlora, Vlora, Albania;4. Institute of Chemistry, Faculty of Science, Sts. Cyril and Methodius University, Skopje, Macedonia;1. CNRS, UMIFRE 21, Department of Ecology, French Institute of Pondicherry, Pondicherry 605001, India;2. School of Mathematics and Statistics, The University of Sheffield, Western Bank Sheffield S10 2TN, United Kingdom;3. UMR 5059 CBAE, Centre de Bio-Archéologie et d’Ecologie, 34 000 Montpellier, France;4. CIRAD UMR TETIS, Maison de la Télédétection, 500 rue J.F. Breton, Montpellier F-34093, France;1. Natural Resources Canada, Canadian Forest Service, Great Lakes Forestry Centre, 1219 Queen Street East, Sault Ste. Marie, ON P6A 2E5, Canada;2. USDA Forest Service, Southern Research Station, Eastern Forest Environmental Threat Assessment Center, 3041 Cornwallis Road, Research Triangle Park, NC 27709, USA;3. Agriculture and AgriFood Canada, 1 Airport Road, Swift Current, SK S9H 3X2, Canada;4. Agriculture and AgriFood Canada, Eastern Cereal and Oilseed Research Centre, 960 Carling Avenue, Ottawa, ON K1A 0C6, Canada;5. Agriculture and AgriFood Canada, Research and Analysis Directorate, Floor 4, Tower 7, 1341 Baseline Road, Ottawa, ON K1A 0C5, Canada;1. Institut de Recherche pour le Développement, UMR 123 AMAP, Laboratory of Applied Botany and Plant Ecology, Conservatoire des Espaces Naturels, Presqu’île de Foué, 98860 Koohnê (Koné), New Caledonia;2. Délégation à la Recherche, Government of French Polynesia, B.P. 20981, Papeete, French Polynesia;3. Université Blaise Pascal, UMR 6042 GEOLAB, 4 Rue Ledru, 63057 Clermont-Ferrand cedex, France |
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| Abstract: | Variables for predicting assemblage differences change as the geographic extent of studies change, hindering development of useful predictive models where study data are limited, or where the chief predictive variables available are fish zones, river size, physiographic regions, ecoregions, hydrologic units, and river basins. In addition, some studies have shown that site-scale predictor metrics have accounted for more of the variation in fish assemblage response metrics than catchment-scale metrics and other studies have shown the reverse. We used cluster analysis on a 780-site database to determine 12–15 aquatic vertebrate clusters at three geographic extents (all 12 conterminous western U.S. states, all western mountain ecoregions, Pacific Northwest mountain ecoregions). Next, we determined predictor variables for those assemblage clusters through use of stepwise discriminant function analysis. Site longitude, site latitude, and catchment dam count were the most significant predictors at the three geographic extents. Site-scale variables represented most of the significant predictors for all three geographic extents, but explained only slightly more aquatic vertebrate assemblage variance than catchment or pure spatial variables. Catchment- and site-scale classification variables accounted for less than half the mean within-cluster similarity demonstrated by the aquatic vertebrate assemblage clusters. We conclude that (a) the large geographic extent of the analysis did not result in catchment-scale predictor variables being more important than site-scale predictors, (b) both catchment- and site-scale variables are important predictors, and (c) existing river basin and ecoregion classifications are useful but insufficient predictors of aquatic vertebrate assemblages. |
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| Keywords: | Aquatic vertebrates Streams Rivers Western USA Assemblage patterns Predictors |
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