The Comparative Demography of Invasive Plants
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The Comparative Demography of Invasive Plants Submitted by Kimberley Jane Jelbert: To the University of Exeter as a thesis for the degree of Doctor of Philosophy in Biological Sciences In June 2018 (uploaded to ORE 3rd Dec 2018) This thesis is available for Library use on the understanding that it is copyright material and that no quotation from the thesis may be published without proper acknowledgement. I certify that all material in this thesis which is not my own work has been identified and that no material has previously been submitted and approved for the award of a degree by this or any other University. (Signature) ……………………………………………………………………………… 1 Abstract Biodiversity, ecosystems, industry and human health are threatened by invasive plant species. The costs of mitigating damages run into billions of pounds per annum. Fundamental to the control of invasive plant species is an ability to predict which species will become invasive. Yet identification of predictive differences between invasive and non-invasive species has proven difficult to pinpoint. In this thesis I identify several weaknesses within published literature, and using field experiments and meta-analyses we address these to find consistent predictors of invasiveness amongst plants. Specifically, I recognize that predictors of invasiveness can be identified by studying plant species in the native range because species may undergo phenotypic and demographic changes following naturalization (Chapters 2 – 5). I also recognize the importance of comparing globally invasive and non-invasive species, and the importance of accounting for phylogenetic relationships so as not to inflate or conceal differences (Chapters 2 – 4). Finally, I investigate whether particular analyses are more appropriate for investigating life history and demographic differences (Chapter 5). This thesis comprises an introductory chapter (Chapter 1), four data chapters (Chapters 2 - 5) and a general discussion (Chapter 6). Chapters 2 and 3 compare life history traits of plant species known to be invasive elsewhere, with their exported but non-invasive sympatric relatives in the native range. Chapter 4 utilizes Population Projection Matrices held within the COMPADRE Plant Matrix Database, to compare demographic projections of stable and transient dynamics of invasive and non-invasive plants; and Chapter 5 compares ten metrics, derived from Population Projection Matrices, of seven invasive species between the native and invaded range to determine if there are demographic or life history differences that facilitate invasion, and to identify those analyses that are most likely to reveal such differences. I find reproductive capacity to be a predictor of invasiveness, and that analyses of transient dynamics are more likely than analyses of projected stable dynamics to reveal demographic or life history differences between invasive and non-invasive species or populations of plants. I 2 discuss these findings in the context of invasive risk assessment protocols and highlight future research opportunities. 3 Acknowledgements I would like to say a massive thank you to Dave Hodgson for giving me the opportunity to undertake a PhD and for being a brilliantly supportive supervisor throughout. It has been an absolute pleasure to work with someone as knowledgeable, patient, passionate and fun as Dave. Secondly (but not secondly by any means) I would like to thank my beautiful, cheeky and intelligent daughter, Emi, for keeping me level headed during difficult times and for tolerating a working mummy. I promise not to change the clocks and trick you into going to bed early anymore (or rather on-time when taking into consideration your expert delaying tactics associated with finding the correct teddy companion)! This strategy was totally necessary to permit PhD progress but still make school pick-up! Thank you to my family, in particular my mum for assisting with Emi care and my dad for encouraging my interest in nature. Also, thank you to my many amazing friends without which getting this far would not have been possible. I cannot list all the varied and fantastic ways that you have helped but needless to say these usually involved wine and chips! Finally I would like to thank my second supervisor, Robbie McDonald, for guidance during the early part of my PhD; co-authors of each data chapter; Cornwall Wildlife Trust and the National Trust for providing access to field sites. This work was funded by the University of Exeter via the University’s Wildlife Research Co- Operative partnership with the Food and Environment Research Agency, now part of the Animal and Plant Health Agency. 4 Table of Contents ABSTRACT _______________________________________________ 2 ACKNOWLEDGEMENTS __________________________________ 4 CHAPTER 1 ______________________________________________ 9 Introduction _________________________________________________________ 9 CHAPTER 2: _____________________________________________ 28 Invasiveness of plants is predicted by size and fecundity in the native range ___ 29 Abstract _______________________________________________________________ 29 Introduction ____________________________________________________________ 30 Materials and Methods ___________________________________________________ 32 Results ________________________________________________________________ 38 Discussion _____________________________________________________________ 43 Author Contributions _____________________________________________________ 48 References _____________________________________________________________ 49 CHAPTER 3: _____________________________________________ 54 Invasive plants escape the tolerance-fecundity trade-off ____________________ 55 Abstract _______________________________________________________________ 55 Introduction ____________________________________________________________ 56 Methods _______________________________________________________________ 60 Results ________________________________________________________________ 66 Discussion _____________________________________________________________ 71 Author Contributions _____________________________________________________ 75 References _____________________________________________________________ 76 CHAPTER 4: _____________________________________________ 81 Demographic predictors of invasiveness, among plants _____________________ 82 Abstract _______________________________________________________________ 82 Main Text ______________________________________________________________ 82 Demographic Syndrome of Invasiveness ______________________________________ 87 Discussion _____________________________________________________________ 90 5 Methods _______________________________________________________________ 92 Author Contributions _____________________________________________________ 98 References _____________________________________________________________ 99 Supplementary Materials _________________________________________________ 104 CHAPTER 5: _____________________________________________175 Adapting to the invaded range: subtle changes in life history cause demographic change in invasive plants _____________________________________________ 176 Abstract ______________________________________________________________ 176 Introduction ___________________________________________________________ 178 Materials & Methods ____________________________________________________ 181 Results _______________________________________________________________ 190 Discussion ____________________________________________________________ 202 Author Contributions ____________________________________________________ 207 References ____________________________________________________________ 208 Supporting Information __________________________________________________ 214 CHAPTER 6: _____________________________________________217 Discussion _________________________________________________________ 217 Our Approach to Invasive Species Research __________________________________ 217 Observations and Recommendations: Management of Invasive Plant Species and Future Research Opportunities __________________________________________________ 222 References ____________________________________________________________ 224 List of Figures Chapter 2: Figure 1 - Chapter 2. Differences in phenotypic and demographic traits between invasive and non- invasive species, in the native range ________________________________________________________________________ 40 Figure 2 - Chapter 2. Differences in phenotypic and demographic traits between invasive and non- invasive species, in the native range ________________________________________________________________________ 41 Figure 3 - Chapter 2. The relationship between basal stem diameter and fecundity ______________________ 42 Chapter 3: 6 Figure 1 - Chapter 3. Differences in seed mass between invasive and non-invasive species, in the native range ________________________________________________________________________________________________________ 67 Figure 2 - Chapter 3. Differences in reproductive investment between invasive and non-invasive species in their native range _________________________________________________________________________________________ 68 Figure 3 - Chapter 3. Differences in reproductive investment between invasive and non-invasive species, in the native range __________________________________________________________________________________________ 69 Figure 4 - Chapter 3. Differences in