Wilfrid Laurier University Scholars Commons @ Laurier Theses and Dissertations (Comprehensive) 2019 Competition or facilitation: Examination of interactions between endangered Sida hermaphrodita and invasive Phragmites australis Samantha N. Mulholland Wilfrid Laurier University, [email protected] Follow this and additional works at: https://scholars.wlu.ca/etd Part of the Botany Commons, Integrative Biology Commons, Other Ecology and Evolutionary Biology Commons, and the Plant Biology Commons Recommended Citation Mulholland, Samantha N., "Competition or facilitation: Examination of interactions between endangered Sida hermaphrodita and invasive Phragmites australis" (2019). Theses and Dissertations (Comprehensive). 2223. https://scholars.wlu.ca/etd/2223 This Thesis is brought to you for free and open access by Scholars Commons @ Laurier. It has been accepted for inclusion in Theses and Dissertations (Comprehensive) by an authorized administrator of Scholars Commons @ Laurier. For more information, please contact [email protected]. Competition or facilitation: Examination of interactions between endangered Sida hermaphrodita and invasive Phragmites australis by Samantha Nicole Mulholland Bachelor of Art, Honours Biology, Wilfrid Laurier University, 2016 THESIS Submitted to the Department of Biology In partial fulfilment of the requirements for the Master of Science in Integrative Biology Wilfrid Laurier University 2019 Samantha Mulholland 2019 © Abstract Virginia Mallow (Sida hermaphrodita) is a perennial herb of the Malvaceae family that is native to riparian habitats in northeastern North America. Throughout most of its geographical distribution however, it is considered threatened and only two populations are known from Canada. The biology and ecology of S. hermaphrodita are still poorly understood and although few studies have been performed to determine the factors that contribute to the species rarity, it is considered threatened potentially due to the loss of habitat caused by exotic European Common reed (Phragmites australis subsp. australis) invasion. Allelopathic and phytotoxic conditioning of soils to inhibit native species are mechanisms that have been proposed to explain the invasion success of P. australis. To quantify the interaction between the two species and assess the capacity for P. australis to inhibit S. hermaphrodita performance through belowground soil modifications, a series of field vegetation surveys were conducted at the Taquanyah Conservation Area during the growing seasons of 2016, 2017, and 2018. Field performance findings suggested that proximity to P. australis had no significant effect on S. hermaphrodita seedling mortality or seedling root arbuscular mycorrhizal colonization. A supplementary greenhouse study was also conducted to examine plant performance and mycorrhizal colonization of both species in soils that correspond to different soil-vegetation levels ranging between pure stands of S. hermaphrodita to pure stands of P. australis in order to determine the potential for P. australis to allelopathically modify soils making them inhospitable for native species. The results provided no evidence to support previous soil conditioning reports since performance and arbuscular mycorrhizal colonization of both species were inversely promoted in their competitor’s soil. Soil nutrient analysis coupled with the plant performance findings suggested that P. australis may not be as strictly competitive as previously believed since evidence of a belowground facilitative interaction between S. hermaphrodita and P. australis has been observed. Based on the results concluding that belowground conditions did not exclude native species, we believe aboveground competition for light is not only the main factor contributing to S. hermaphrodita’s limited distribution where it occurs with P. australis, but also key to the invasion success of P. australis. i Future research and management treatments focussed on disrupting P. australis’ competitive exclusion of light would be beneficial to the recovery of endangered species like S. hermaphrodita. ii I would like to dedicate this thesis in loving memory of my grandfather, who was the first to teach me the value of appreciating the plants around me and will remain one of my biggest inspirations. John Valentine Mulholland D.F.C. February 14, 1922 – June 2, 2017 iii Acknowledgements I would like to firstly express my gratitude to my supervisors Dr. Mihai Costea and Dr. Kevin Stevens for giving me this opportunity and for their patience and guidance throughout this M.Sc. I would also like to thank my committee members Dr. Rebecca Rooney and Dr. Eric Snyder for their input and suggestions which have been very valuable during the completion of this project. Additionally, I would like to thank both Dr. Derek Gray for his beneficial comments as external examiner and Dr. Stephanie DeWitte-Orr for her excellent involvement as the defense chair. I am very grateful for the funding provided for this project by the Government of Ontario through the Species at Risk Research Grant and also for the support of the Grand River Conservation Authority who provided continuous access to the Taquanyah Conservation Area where this research was completed. Thank you also to the numerous students and research assistants of the Stevens lab who braved the overwhelming conditions at Taquanyah to assist with field sampling during this study, with very special thanks to Kayla Salive, Rebekah Hamp and Rachel Tzeckas for being constantly available for me to rely on throughout the entirety of this project when I needed any assistance. Last but not least, I am extremely grateful to my family and friends. To my parents Dave and Jackie as well as my sister Tiffany, thank you for being my biggest supporters and for providing me more assistance than I ever imagined I would need. To my friends Sunny Choi, Megan Bott, Jenell Hogg, Anna Slepova and Curtis Black, thank you so much for your continuous positivity, encouragement and comic relief when I needed an escape from my stress. I cannot thank you all enough because I honestly wouldn’t have gotten through this project without you. iv Table of Contents Abstract i Acknowledgements iv List of Tables viii List of Figures x Chapter 1: General Introduction 1 1.1 Biology, Ecology and Conservation Status of Sida hermaphrodita 1 1.1.1 Name and taxonomic history 1 1.1.2 Plant description 2 1.1.3 Geographical distribution in North America 3 1.1.4 Geographical distribution outside North America 4 1.1.5 Conservation status in North America 5 1.1.5.1 Canada 5 1.1.5.2 U.S.A. 5 1.1.5.3 Factors contributing to its rarity 5 1.1.6 Habitat and vegetation 6 1.1.7 Growth and development 7 1.1.8 Mycorrhiza 8 1.1.9 Physiology 10 1.1.10 Reproduction 10 1.1.10.1 Floral biology 10 1.1.10.2 Potential for vegetative reproduction 11 1.1.10.3 Seed dispersal 11 1.1.10.4 Viability of seeds and germination 11 1.1.11 Population dynamics 12 1.1.12 Responses to herbicides and other chemicals 13 1.1.13 Responses to herbivory and diseases 13 1.2 Biology and Interactions of Phragmites australis 15 1.2.1 Name and taxonomic history 15 1.2.2 Plant description 15 1.2.2.1 Interspecific variation 16 1.2.3 North American geographical distribution and habitat 17 1.2.3.1 Native 18 v 1.2.3.2 Gulf coast 19 1.2.3.3 Invasive 20 1.2.4 Growth, development and reproduction 21 1.2.4.1 Intraspecific hybridization 23 1.2.5 Mycorrhiza 24 1.2.6 Potential invasion mechanisms 25 1.3 Objectives and Hypotheses 30 1.4 Figures 32 1.5 References 34 Chapter 2: Seedling performance of endangered Sida hermaphrodita does not support a putative detrimental soil conditioning by Phragmites australis 47 2.1 Abstract 48 2.2 Introduction 48 2.3 Materials and Methods 51 2.3.1 Site description 51 2.3.2 Field seedling vegetation survey 52 2.3.3 Seedling collection 53 2.3.4 AMF assessment 54 2.3.5 Statistical analyses 54 2.4 Results 55 2.4.1 Seedling performance 55 2.4.2 Seedling AMF colonization 56 2.5 Discussion 57 2.5.1 Seedling performance 58 2.5.2 Seedling AMF colonization 60 2.5.3 Synthesis of detrimental interaction 60 2.6 Tables and Figures 63 2.7 Supplemental Information 78 2.8 References 88 Chapter 3: Reciprocal belowground facilitation not allelopathic inhibition occurs between invasive Phragmites australis and endangered Sida hermaphrodita 96 3.1 Abstract 98 3.2 Introduction 98 3.3 Materials and Methods 101 vi 3.3.1 Site description 101 3.3.2 Soil collection and nutrient analyses 101 3.3.3 Soil core experimental design 102 3.3.4 Seed germination, seedling planting and harvest 103 3.3.5 AMF assessment 104 3.3.6 Statistical analyses 104 3.3 Results 105 3.3.1 Sida hermaphrodita and Phragmites australis plant growth response 105 3.3.2 AMF colonization 107 3.3.3 Soil nutrient composition correlations 109 3.4 Discussion 110 3.5 Acknowledgements 116 3.6 Tables and Figures 117 3.7 Supplemental Information 137 3.8 References 147 Chapter 4: General discussion 154 4.1 Summary of main research findings 154 4.2 Main conclusions 155 4.3 Integration and collaboration 157 4.4 Future directions and conservation implications 159 4.5 Figures 163 4.6 References 166 vii List of Tables Table 2.1: Output of two-way ANOVA used to assess interactions between survey year and P. australis proximity level and their effect on S. hermaphrodita seedling performance .............................................. 63 Table 2.2: Output of one-way ANOVA used to assess preliminary relationships between S. hermaphrodita seedling root arbuscular mycorrhizal colonization and P. australis proximity level ......... 64 Table 2.3: Output of two-way ANOVA used to assess interactions between survey month and P. australis proximity level and their effect on S. hermaphrodita seedling arbuscular mycorrhizal colonization ........ 65 Table S2.1: Classification of all plant species identified within quadrats set up at Taquanyah Conservation Area where vegetation surveys were conducted in different P.