Modeling the potential North American distribution of Russian olive, an invader of riparian ecosystems

Abstract

Russian olive (Elaeagnus angustifolia L., Elaeagnaceae) has gained notoriety as an invasive tree in the United States (US), particularly owing to its impacts within western riparian ecosystems. In Canada, its potential for range expansion has yet to be assessed, despite alarming infestations in parts of southern British Columbia (BC). Existing niche model predictions are of limited utility because they are restricted to the US, were constructed in the absence of higher latitude records in Canada, and did not consider potentially important soil-related predictors. Here, we address these gaps, and include more than 1400 new occurrence records for Canada, most of which were collected using Google Street View. Our Maxent niche models achieved excellent performance (AUC > 0.9), and identified mean temperature of the coldest quarter and topsoil pH as the first and second-most important predictor variables, respectively, neither of which was included in previously published niche models. High habitat suitability is predicted in areas of western Canada that presently lack occurrence records, including along several major rivers in south-central BC. Our findings should prove valuable to nascent detection and management efforts in western Canada, and also highlight the benefits of basing niche model predictions on occurrence records encompassing as much of the invaded range as possible.