Reproductive Ecology of Bird-Pollinated Babiana (Iridaceae): Floral Variation, Mating Patterns and Genetic Diversity
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REPRODUCTIVE ECOLOGY OF BIRD-POLLINATED BABIANA (IRIDACEAE): FLORAL VARIATION, MATING PATTERNS AND GENETIC DIVERSITY by Caroli de Waal A thesis submitted in conformity with the requirements for the degree of Master of Science Department of Ecology and Evolutionary Biology University of Toronto © Copyright by Caroli de Waal 2010 REPRODUCTIVE ECOLOGY OF BIRD-POLLINATED BABIANA (IRIDACEAE): FLORAL VARIATION, MATING PATTERNS AND GENETIC DIVERSITY Caroli de Waal Master of Science Department of Ecology and Evolutionary Biology University of Toronto 2010 Abstract Flowering plants possess striking variation in reproductive traits and mating patterns, even among closely related species. In this thesis, I investigate morphological variation, mating and genetic diversity of five taxa of bird-pollinated Babiana (Iridaceae), including two species with specialized bird perches. Field observations in 12 populations demonstrated that sunbirds were the primary pollinators. Babiana ringens exhibited correlated geographic variation in flower and perch size. Controlled field pollinations revealed self-compatibility and low pollen limitation in B. ringens subspecies, and self-incompatibility and chronic pollen limitation in B. hirsuta. Allozyme markers demonstrated moderate to high selfing rates among populations and considerable variation in levels of genetic diversity. In B. ringens there was a positive relation between the geographic and genetic distance of populations. The results of a manipulative field experiment indicated position-dependent herbivory on inflorescences of B. hirsuta and this could play a role in the evolution of specialized bird perches in Babiana. ii Acknowledgments First, I would like to thank my supervisor Spencer Barrett for his wealth of knowledge, his contagious enthusiasm about the natural world, and for pushing me further than I thought I could go. I have learned much from his wonderful writing and editorial skills and his advice on how to be a better scholar. I truly appreciate his guidance and support, and his generosity of spirit. I am greatly indebted to Bruce Anderson for his large contribution to many of the ideas explored in my thesis, and his advice and comments during the writing process. Bruce opened my eyes to many interesting aspects of the Cape flora, and I learned much from his exciting approaches to field work and experimental design. Thank you to my supervisory committee James Thomson, Stephen Wright, and John Stinchcombe for their valuable input and guidance throughout my time at the University of Toronto. Many thanks to James Thomson, Helen Rodd, Megan Frederickson and Bruce Anderson for their participation, advice and comments during my defense exam. A very big note of thanks to Bill Cole who, with the greatest patience and calmness, taught me all I know about allozymes and assisted me in the lab, and provided so much help with statistical analyses, figures, maps, general advice and logistics. Thank you to Melinda Pickup and Sarah Yakimowski for statistical advice, and to Mathieu Siol for his help with the population genetics section and improving my understanding of genetic parameters, as well as his help with formatting references. The research in this thesis was funded by an NSERC Discovery Grant and funds from the Canada Research Chair‟s Program, both to Spencer C.H. Barrett, and a Connaught Scholarship awarded to Caroli de Waal. Many people assisted me during three and a half months of field work in South Africa. I would like to acknowledge the Department of Botany and Zoology at the University of Stellenbosch, South Africa, for providing research space and resources. I am very grateful to S.P. and Lauriëtte de Waal, Darius van Rensburg, Anina Heystek, and Bruce Anderson for field assistance. Anina was particularly helpful with fruit and seed counting. John Manning (South African National Biodiversity Institute, Kirstenbosch Research Centre, Cape Town) and the staff at the Compton Herbarium were most helpful in providing information about bird- pollinated Babiana species, and in particular the exact localities of B. carminea and B. iii avicularis. Thank you to Janet Naudé for providing the locality of STIL, Nico de Jager and Niekie de Jager for localities of VIC1 and VIC2 on their farm Victoriasdal, Marnus Truter for the locality of HOPE on his farm Koperfontein, Jakkie van der Westhuizen for permission to work in the B. avicularis population on his farm, Claire for the locality of RED, Bruce Anderson for localities of SCAR, ELA, LAM, and MAM, and Ronderberg Private Nature Reserve and Jongensgat Private Nature Reserve for permission to work on their properties. S.P. de Waal and his colleagues were most helpful in providing maps and GPS services. Many people contributed to my wonderful experience at the University of Toronto. In particular the lovely people I met in the Barrett lab: Melinda Pickup, David Field, Sarah Yakimowski, Mathieu Siol, Rob Ness, Bill Cole, and past members Rob Colautti and Jannice Friedman. I appreciate all your support and friendship and I have truly learned from each one of you. I will always cherish all the fun times we shared together! Thank you to my office mates, especially Andrea Zikovitz, for good cheer and giggles in the office. Thanks to Allison Kwok for early morning snacks, Jane Ogilvie and Alison Parker for their caring natures, and all my other friends in the department. I am so grateful to Sarah Yakimowski for her generous and inspiring friendship. A special note of thanks to Florence Deau, Mathieu Siol, and baby Timon for always making me smile, and for being there when I needed a friend. Many friends in other parts of the world provided continuous encouragement, especially Erika and Andy Beahm and Marésa Lotter. My deepest gratitude to my family in South Africa, and most of all my parents, S.P. and Lauriëtte de Waal, who stood on the side lines cheering me on; always offering their unconditional love and support and prayers. iv Table of Contents LIST OF TABLES ix LIST OF FIGURES xi LIST OF APPENDICES xiv CHAPTER 1 – GENERAL INTRODUCTION 1 POLLINATION SYSTEMS 2 MATING SYSTEMS 5 STUDY SPECIES 6 SPECIFIC OBJECTIVES OF THIS THESIS 16 CHAPTER 2 – FLORAL BIOLOGY OF BIRD-POLLINATED BABIANA (IRIDACEAE) 18 ABSTRACT 18 INTRODUCTION 19 MATERIALS AND METHODS 24 Study sites 24 Pollinator observations 24 Variation in morphological traits 25 Statistical analysis 28 RESULTS 29 v Pollinator observations 29 Trait variation among taxa 33 Trait correlations 37 Geographical variation in perch and flower traits in Babiana ringens and a comparison with B. avicularis 40 Apical flowers in Babiana ringens and B. avicularis populations 47 DISCUSSION 49 Bird pollination in Babiana 49 Variation in floral and nectar traits 54 Geographical patterns of trait variation in Babiana ringens 55 CHAPTER 3 – MATING, FERTILITY AND PATTERNS OF GENETIC DIVERSITY IN BIRD-POLLINATED BABIANA SPECIES (IRIDACEAE) 60 ABSTRACT 60 INTRODUCTION 61 MATERIALS AND METHODS 64 Fertility studies 64 Estimates of mating patterns 67 Measures of genetic diversity and relationships among populations 69 RESULTS 70 Components of fertility in bird-pollinated Babiana 70 Compatibility 71 vi Autonomous self-pollination 74 Pollen limitation 77 Contribution of autogamy to self-fertilization 78 Mating patterns 78 Genetic diversity 79 Geographical and genetic relationships among populations 81 DISCUSSION 83 Self- versus cross-fertilization 85 Pollen limitation of fertility 87 Patterns of mating 88 Patterns of genetic variation 90 Geographical variation and genetic divergence 91 CHAPTER 4 – MAMMALIAN HERBIVORY AND THE EVOLUTION OF A SPECIALIZED BIRD PERCH 94 ABSTRACT 94 INTRODUCTION 95 MATERIALS AND METHODS 99 Study sites 99 Surveys of herbivory 99 Field experiment comparing reproductive success of apical versus basal flowers 100 vii Data analysis 104 RESULTS 104 Evidence and effects of herbivory 104 Effects of herbivory on the reproductive success of apical versus basal flowers 106 DISCUSSION 110 Antagonistic effects of herbivory 110 Evolution of a specialized bird perch in Babiana 112 CHAPTER 5 – GENERAL CONCLUSIONS 114 FLORAL BIOLOGY OF BIRD-POLLINATED BABIANA 114 MATING, FERTILITY AND PATTERNS OF GENETIC DIVERSITY IN BIRD- POLLINATED BABIANA 115 MAMMALIAN HERBIVORY AND THE EVOLUTION OF A SPECIALIZED BIRD PERCH 116 FUTURE APPROACHES 116 LITERATURE CITED 121 viii List of Tables Table 2.1. Bird observations in three populations of Babiana ringens subsp. ringens, four populations of B. ringens subsp. australis, three populations of B. hirsuta, one population of B. avicularis, and one population of B. carminea. 31 Table 2.2. Mean percentage of flowers per plant showing signs of nectar robbery by birds. 32 Table 2.3. Means, standard errors, and sample sizes of 14 morphological traits measured in 15 populations of bird-pollinated Babiana species. 35 Table 2.4. Within-taxon Pearson product-moment correlation coefficients based on individual measurements pooled across all populations of each taxon for eight morphological characters of Babiana ringens subsp. ringens, B. ringens subsp. australis, and B. avicularis measured in 11 populations in the Western Cape Province of South Africa. 38 Table 2.5. Within-taxon Pearson product-moment correlation coefficients based on individual measurements pooled across populations of each taxon for six morphological characters of Babiana hirsuta and B. carminea measured in four populations in the Western Cape Province of South Africa. 39 Table 3.1. Sample sizes per treatment in experiments