An ecological assessment of Russian olive in western Canada : predicted distribution across its invaded range and insect associations in southern BC

Russian olive is a small tree or large multi-stemmed shrub that was introduced to Canada and the United States (US) from Eurasia in the early 1900s. It was provisioned in large numbers during the last century to prairie farmers as a shelterbelt plant, and remains a popular and widely-available ornamental. Now invasive within some riparian ecosystems in the western US, Russian olive has been declared noxious in the states of Colorado and New Mexico. With traits including high shade tolerance and a symbiotic association with nitrogen-fixing bacteria, Russian olive has the potential to dominate riparian vegetation, and thus radically transform riparian ecosystems. Despite its naturalization in many parts of Canada, especially in the south-west, little is known about its potential invasion range or impact within Canadian ecosystems. In this thesis, I conducted a 3 part ecological assessment of Russian olive in Canada. First, I critically evaluated the potential for Russian olive to become invasive and problematic within riparian ecosystems in Canada. Second, I predicted the potential distribution of Russian olive in North America through ecological niche modeling, building substantially upon previous work by using ecologically relevant predictors and North American occurrence records. I found that Russian olive has not yet filled its potential range within North America, including riparian zones along economically important salmon-bearing rivers and streams in southern British Columbia. Third, I conducted the first standardized assessment of insect assemblages on Russian olive in comparison to two co-occurring native shrubs species, Woods’ rose and Saskatoon. I found that the insect family richness, diversity, community composition and community variance were no different from that of co-occurring native shrubs. These findings are consistent with a neutral response of insects to Russian olive compared to co-occurring native shrubs. The findings of this research will help guide management plans for Russian olive in Canada.Arts and Sciences, Irving K. Barber School of (Okanagan)Biology, Department of (Okanagan)Graduat