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Systematics of Dyerophytum (Plumbaginaceae) with a focus on heterostyly and the evolution of endemic taxa from Socotra Rachael Graham 20th August 2014 Thesis submitted in partial fulfilment for the MSc in the Biodiversity and Taxonomy of Plants Abstract Dyerophytum is shown to be a monophyletic genus consisting of four morphologically distinct species, and is placed in the Plumbaginoideae subfamily of Plumbaginaceae. Dyerophytum is placed as sister to a main clade of Plumbago, but this relationship is complicated by the unexpected sister relationship of Plumbago europaea to the monotypic genus Plumbagella micrantha. Within Dyerophytum, Dyerophytum africanum is placed as the earliest diverging lineage, while the two Socotran species form a clade sister to Dyerophytum indicum. Dating analysis estimates the origin of the Socotran clade to 1.82 MYA (0.71-3.10 MYA), which is much more recent than the current estimate for the separation of Socotra from the Arabian Peninsula, at approximately 18 MYA. This recent date strongly supports an origin of Dyerophytum on Socotra by long distance dispersal from Asia/Arabia, and adds to growing evidence supporting the role of both dispersal and vicariance in shaping the Socotran flora. Dyerophytum africanum and Dyerophytum indicum are confirmed to show dimorphic exine sculpturing which is characteristic of heterostyly. Pollen in the Socotran species appears to be monomorphic, indicating that heterostyly has been lost in this lineage, which is hypothesised to be the result of selective pressure on island colonisers to be self-compatible. Acknowledgements Firstly, I would like to thank Alan Forrest for his guidance and support throughout this project. Secondly, I would like to thank the many people who have assisted with the technical aspects of the project: Tiina Sarkinen for guidance and troubleshooting with the phylogenetic analyses, Frieda Christie for technical support and advice with scanning electron microscopy, Elspeth Haston for support with the herbarium work, and also Michelle Hollingsworth and Laura Forrest for the excellent training provided in molecular techniques. Thirdly, I wish to thank my fellow MSc students who have been so generous in sharing their valuable knowledge (and excellent cake). Lastly, I thank my family who have been so supportive of my academic ambitions, and always suspected that the girl with leaves and feathers in her pockets would grow up to be a scientist one day. Table of Contents Abstract Acknowledgements 1. Introduction……………………………………………………………………….….1 1.1. General Introduction……………………………………………………………1 1.2. Introduction to Plumbaginaceae………………………………………………..1 1.3. Introduction to Dyerophytum…………………………………………………...3 1.4. Introduction to Heterostyly……………………………………………………..5 1.4.1. History and Definition………………………………………………...…5 1.4.2. Floral Polymorphisms…………………………………………………....7 1.4.3. Genetic Basis of Heterostyly……………………………………………..9 1.4.4. Origins of Heterostyly…………………………………………………..11 1.4.5. Evolution of Heterostyly…………………………………………….….11 1.4.6. Heterostyly in Plumbaginaceae………………………………………...13 1.5. Introduction to Socotra………………………………………………………...16 1.5.1. Geology and Climate……………………………………………………16 1.5.2. Endemism and Vegetation Types………………………………………18 1.5.3. Floristic Affinities……………………………………………………….19 1.5.4. Biogeographic Patterns……………………………………………..…..20 1.6. Hypotheses and Aims of Project…………………………………..…………..23 2. Materials and Methods……………………………………………………….…….26 2.1. Taxonomic Sampling…………………………………………………...………26 2.2. Molecular Techniques……………………………………….…………………26 2.3. Phylogenetic Analysis…………………………………………………………..28 2.4. Molecular Dating Analysis……………………………………...……………..29 2.5. Morphology……………………………………………………………………..30 2.5.1. Character Analysis………………………………………………...……30 2.5.2. Scanning Electron Microscopy………………………………...………33 3. Results……………………………………………………………………………….34 3.1. Phylogenetic Analysis…………………………………………………………..34 3.1.1. Combined Plastid Analysis…………………………………………..…36 3.1.2. ITS Analysis…………………………………………………………..…38 3.1.3. Combined Plastid and Nuclear Analysis………………………..……..40 3.2. Molecular Dating Analysis………………………………………………….....42 3.3. Morphometric Ordination Analysis…………………………………….…….44 3.4. Scanning Electron Microscopy………………………………………….…….48 4. Discussion……………………………………………………………………………57 4.1. Phylogenetic Position of Dyerophytum……………………………………...…57 4.2. Relationships in Dyerophytum……………………………………………...….58 4.3. Biogeography…………………………………………………………………...60 4.4. Morphological Characters……………………………………………………..66 4.5. Taxonomy……………………………………………………………………….69 4.6. Heterostyly……………………………………………………………………...73 5. Conclusions………………………………………………………………………….77 6. Taxonomic Revision………………………………………………………………...78 7. References…………………………………………………………………………...82 8. Appendix…………………………………………………………………………….96 List of Figures Figure 1.4.1.a: Diagram showing difference in length of style and stamens in distylous flowers Figure 1.4.1.b: Diagram showing difference in length of style and stamens in tristylous flowers Figure 1.4.2.a: Diagram showing difference in morphology of stigmatic papillae between papillate and cob stigmas Figure 1.5.1.a: Map showing location of the islands of the Socotra archipelago Figure 2.5.1.a: Diagrams showing morphological characters measured Figure 3.1.1.a: Bayesian consensus tree for combined plastid dataset. Figure 3.1.2a: Bayesian consensus tree for ITS dataset Figure 3.1.3a: Bayesian consensus tree for combined plastid and nuclear dataset Figure 3.2.a: Dated maximum clade credibility tree for combined plastid and nuclear dataset Figure 3.3.a: PCA analysis showing principal components 1 and 2 Figure 3.3.b: PCA analysis showing principal components 1 and 3 Figure 3.3.c: PCA analysis showing principal components 2 and 3 Figure 3.4.a: Electron micrographs of pollen grains in Dyerophytum africanum (collection no. 127) Figure 3.4.b: Electron micrographs of pollen grains in Dyerophytum africanum (collection no. 6371) Figure 3.4.c: Electron micrographs of pollen grains in Dyerophytum indicum (collection no. 729) Figure 3.4.d: Electron micrographs of pollen grains in Dyerophytum indicum (collection no. 2251) Figure 3.4.e: Electron micrographs of pollen grains in Dyerophytum pendulum (collection no. 217) Figure 3.4.f: Electron micrographs of pollen grains in Dyerophytum pendulum (collection no. 14041) Figure 3.4.g: Electron micrographs of pollen grains in Dyerophytum socotranum (collection no. 359) Figure 3.4.h: Electron micrographs of pollen grains in Dyerophytum socotranum (collection no. 8684) Figure 4.3.a: Distribution map of Dyerophytum pendulum on Socotra Figure 4.3.b: Distribution map of Dyerophytum socotranum on Socotra Figure 4.3.c: Geological map of Socotra Figure 4.5.a: Photographs showing representative leaf shapes in herbarium specimens of Dyerophytum Figure 4.5.b: Photographs showing representative floral morphology in herbarium specimens of Dyerophytum List of Tables Table 2.2.a: Primers used in this study Table 2.5.1.a: List of characters measured for morphometric analysis Table 3.1.a: Summary of alignment statistics Table 3.3.a: Contributions of morphological characters to each principal component Table 3.3.b: Eigenvalues and percentage variance accounted for by each principal component Table 4.4.a: combinations of character states in Dyerophytum indicated by PCA analysis List of Appendices 8.1: Provenance and voucher information for DNA samples extracted 8.2: Accession numbers of sequences downloaded from GenBank 8.3: List of herbarium specimens included in morphometric analysis and in taxonomic revision 8.4: Provenance and voucher information for samples studied using SEM 8.5: Morphometric data used in PCA analysis 8.6: Summary statistics for morphometric data 1. Introduction 1.1. General Introduction This is a study of the evolution of Dyerophytum, concentrating on the evolution of insular endemic taxa from Socotra. This will include an analysis of species level systematics of Dyerophytum and its position within the wider Plumbaginaceae phylogeny. As part of this, a morphometric analysis and taxonomic revision will be carried out to delimit taxa and establish the correct names to be applied. In addition, the systematic analysis will provide a framework to allow an analysis of the biogeographic history of Dyerophytum. Investigation will also be carried out into pollen heteromorphism in Dyerophytum in an effort to understand the evolution of heterostyly in this genus. 1.2. Introduction to Plumbaginaceae Juss. The Plumbaginaceae family consists of around 27 genera and 650 species (Kubitzki, 1993), although it has been suggested that there may be in excess of 1000 species (Lledo, et al., 1998). Most species are shrubs, climbers or herbs with simple, exstipulate, spirally arranged leaves which often have secretory glands on their surface (Heywood, 1993). Plumbaginaceae has a cosmopolitan distribution, with representatives in the temperate and tropical Old and New World as well as in the Southern Hemisphere, but appears to have its centre of diversity in the mountains of central Asia (Kubitzki, et al., 1993) The family primarily grows in cool alpine areas, and also in saline coastal areas where they are often a dominant component of the vegetation (Heywood, 1993). Plumbaginaceae is recognised as a highly stress tolerant and halophytic plant family (Hanson, et al., 1994) and many of its species are adapted to their saline habitat by the presence of excretory salt glands (Liphschitz & Waisel, 1982). The family is generally considered monophyletic on the basis