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Challenges of predicting the potential distribution of a slow-spreading invader: a habitat suitability map for an invasive riparian tree


Understanding the potential spread of invasive species is essential for land managers to prevent their establishment and restore impacted habitat. Habitat suitability modeling provides a tool for researchers and managers to understand the potential extent of invasive species spread. Our goal was to use habitat suitability modeling to map potential habitat of the riparian plant invader, Russian olive (Elaeagnus angustifolia). Russian olive has invaded riparian habitat across North America and is continuing to expand its range. We compiled 11 disparate datasets for Russian olive presence locations (n = 1,051 points and 139 polygons) in the western US and used Maximum entropy (Maxent) modeling to develop two habitat suitability maps for Russian olive in the western United States: one with coarse-scale water data and one with fine-scale water data. Our models were able to accurately predict current suitable Russian olive habitat (Coarse model: training AUC = 0.938, test AUC = 0.907; Fine model: training AUC = 0.923, test AUC = 0.885). Distance to water was the most important predictor for Russian olive presence in our coarse-scale water model, but it was only the fifth most important variable in the fine-scale model, suggesting that when water bodies are considered on a fine scale, Russian olive does not necessarily rely on water. Our model predicted that Russian olive has suitable habitat further west from its current distribution, expanding into the west coast and central North America. Our methodology proves useful for identifying potential future areas of invasion. Model results may be influenced by locations of cultivated individuals and sampling bias. Further study is needed to examine the potential for Russian olive to invade beyond its current range. Habitat suitability modeling provides an essential tool for enhancing our understanding of invasive species spread.

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We would like to thank the many people who donated datasets to our research efforts especially the Southwest Exotic Plant Mapping Program, the Utah BLM office, the Colorado Department of Transportation, Pat Shafroth and Jonathan Freidman. We thank the National Park Service, Colorado State University and the US Geological Survey Fort Collins Science Center for logistical support. We thank Jonathan Friedman and Tom Stohlgren for providing comments on an earlier version of our manuscript. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Two anonymous peer reviewers provided additional comments. To all we are grateful.

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Correspondence to Catherine S. Jarnevich.

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Jarnevich, C.S., Reynolds, L.V. Challenges of predicting the potential distribution of a slow-spreading invader: a habitat suitability map for an invasive riparian tree. Biol Invasions 13, 153–163 (2011).

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  • Biological invasions
  • Exotic plant species
  • Habitat suitability model
  • Maxent
  • Riparian
  • Russian olive