An Ecological Assessment of Russian Olive in Western Canada: Predicted Distribution Across Its Invaded Range and Insect Associations in Southern BC
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An ecological assessment of Russian olive in western Canada: Predicted distribution across its invaded range and insect associations in southern BC by LIANA KELSEY DIANE COLLETTE B.Sc. (with Great Distinction), University of Lethbridge, 2012 A THESIS SUBMITTED IN PARTIAL FULFULLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in THE COLLEGE OF GRADUATE STUDIES (Biology) THE UNIVERSITY OF BRITISH COLUMBIA (Okanagan) AUGUST 2014 © Liana Kelsey Diane Collette, 2014 Abstract 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. ii Preface The research in this thesis was designed, performed, analyzed, and written by me, Liana Collette, in collaboration with my supervisory committee, Drs. Jason Pither, Robert Lalonde, and Rosemarie De Clerck-Floate. Insect and Russian olive occurrence data were collected with the help of Emma Walker and Prairie Shelterbelt Program Russian olive planting data were obtained from Darren Bruhjell (Agriculture and Agri-Food Canada). iii Table of Contents Abstract ................................................................................................................................... ii Preface ................................................................................................................................... iii Table of Contents ................................................................................................................... iv List of Tables .......................................................................................................................... vi List of Figures ........................................................................................................................ vii Acknowledgements ..................................................................................................................x Chapter 1: Introduction ..........................................................................................................1 1.1 General introduction ......................................................................................................1 1.2 Russian olive biology ......................................................................................................2 1.3 Russian olive distribution: past and present................................................................5 1.4 Ecological impacts ........................................................................................................10 1.5 Potential for management and control .......................................................................14 1.6 Anticipated impacts and future research needs ........................................................15 1.7 Summary .......................................................................................................................20 1.8 Research outline and objectives ..................................................................................20 Chapter 2: Predicting the potential invasion range of Russian olive in North America .22 2.1 Background ...................................................................................................................22 2.2 Methods and Materials ................................................................................................25 2.3 Results ...........................................................................................................................35 2.4 Discussion ......................................................................................................................45 Chapter 3: Insect assemblages associated with the exotic riparian shrub Russian olive, and co-occurring native shrubs ............................................................................................53 3.1 Background ...................................................................................................................53 3.2 Methods and Materials ................................................................................................57 3.3 Results ...........................................................................................................................62 3.4 Discussion ......................................................................................................................67 Chapter 4: Conclusion ...........................................................................................................73 4.1 General discussion ........................................................................................................73 4.2 Applications ..................................................................................................................74 4.3 Assumptions and limitations .......................................................................................75 iv 4.4 Future directions ..........................................................................................................77 Works Cited ............................................................................................................................80 Appendices ............................................................................................................................102 Appendix A – Supplementary figures and tables for Russian olive ecological niche modeling ............................................................................................................................102 Appendix B – Insect assemblages on Russian olive, Rose, and Saskatoon .................107 v List of Tables Table 1.1 Ecozones, natural habitats and habitat requirements of Russian olive and its confamilials in Canada .......................................................................................3 Table 2.1 Sources of georeferenced Russian olive locations in Canada and the US .......26 Table 2.2 Predictor variables used to derive the total and US dataset models ................31 Table 2.3 The average results for the Maxent ENMs showing the test AUC, the AUC standard deviation, the 10 percentile training presence test omission rate, the 10 percentile training presence threshold, and the amount of area predicted suitable and unsuitable for both models...........................................................43 Table 3.1 Site descriptions and number of host plant types sampled per site. Longitude and latitude are decimal degree values (WGS 1984 datum) ............................59 Table 3.2 Comparison of insect families unique to Russian olive in this study to insect families found on Russian olive in the Pendleton et al. (2011) study ..............69 Table A1 Pearson correlation coefficient (r) matrix of all predictors considered for ENM modeling...............................................................................................102 Table B1 Insect families found solely on each plant type .............................................107 Table B2 Abundance of adult insect orders and families found on each plant type during each sampling period (June, July, and August) .......................... 108-110 vi List of Figures Figure 1.1 Phylogenetic tree of the order Rosales...............................................................2 Figure 1.2 Number of Russian olive seedlings planted through the Prairie Shelterbelt Program ..............................................................................................................7 Figure 1.3 The years in which Russian olive was planted through the Prairie Shelterbelt Program ..............................................................................................................8