The copyright of this thesis vests in the author. No quotation from it or information derived from it is to be published without full acknowledgementTown of the source. The thesis is to be used for private study or non- commercial research purposes only. Cape Published by the University ofof Cape Town (UCT) in terms of the non-exclusive license granted to UCT by the author. University Testing the adaptive nature of morphological diversification in the hemiparasitic genus Thesium L. (Santalaceae) Timothy Eoin Moore MRXTIM001 Thesis presented for the degree of Master of Science Town In the Department of Botany University of Cape Town Cape Februaryof 2011 Supervisors UniversityDr GA Verboom, Assoc Prof MD Cramer Town Thesium euphorbioidesCape by GA Verboom of University i Plagiarism declaration I know the meaning of plagiarism and declare that all of the work in this thesis, save for that which is properly acknowledged, is my own Signed: Date: Town Cape of University ii Acknowledgements First and foremost thanks must go to my supervisors, G Anthony Verboom and Michael D Cramer, for their patience and understanding. I have learned so much thanks to their experience and the range of technical abilities that they have acquired over the years. I am also extremely grateful to Félix Forest for his assistance and guidance during my time in the Jodrell Labratory at Kew. Thanks must also go to the technical staff in the Botany Department at UCT. Special thanks must go to Mr Edward Chirwa, Mr Desmond Barnes and Ms Sandy Smuts. Thanks also to Mr Ian Newton for assistance with my isotopic analysis, and to Ms Edith Kapinos and Mr David Macaya-Sanz and the rest of the staff in the Jodrell. Special mention must also go to the people who helped me enormously with my extensive, and sometimes tiring, field work, thanks to Charles Stirton, Terry Trinder-Smith and Rob Skelton without whose help the Bolus Herbarium would have far fewer Thesium specimens. To my officemates, Julia and Roland, thanks for putting up with my periodic ranting. Thanks to Japser Slingsby for help with R. To all my friends and family who have kept me relatively sane over the last few years, thank you for your support. I will never be able to repay youTown for your love and kindness. Thanks to the National Research Foundation and RoyalCape Botanic Gardens, Kew for personal and project funding. Thanks also to the Harry Crossley and Siri Johnson Foundations and the Dorothy Cameron Scholarship for personalof funding. University iii Abstract Much attention has been given to the potential role of edaphic heterogeneity in promoting functional divergence and even speciation in the CFR. The ability to tap into the resources of surrounding hosts may enable parasitic plants to overcome deficiencies in the availability of soil nutrients and, as such, parasitism may represent an adaptation to low-nutrient environments. The hemiparasitic genus Thesium (Santalaceae) offers an excellent opportunity for studying the potential role of edaphic heterogeneity in promoting divergence in specialized resource acquisition/utilization, and its consequences for speciation, in Cape plants. Thesium is a large, widely distributed genus of root hemiparasites in the CFR, occurring on all major substrates, although it seems to favour acidic, sandstone-derived soils. Within the CFR, Thesium shows remarkable diversity in growth form, particularly with regard to traits associated with carbon acquisition. This thesis tests the hypothesis that parasitism in Thesium represents a specialised foraging strategy for dealing with the nutrient poor soils found in the CFR. Specifically, I set out to test the hypothesis that Thesium represents a classic example of a Cape plant radiation with both functional and taxonomic diversification being driven by adaptation to environments of differentTown fertility. The data are presented in two chapters, the first of which deals with the phylogeny of Thesium and the second with the functional significance of trait divergence. Results of a dating analysis on a molecular phylogeny comprising of 72 Thesium species suggests that the radiation leading to the extant diversity of Cape species occurred approximatelyCape 17 Mya. In chapter two, correlative analyses using both raw and phylogeneticallyof independent (PIC) data show that divergence within the Cape clade in the degree of heterotrophy as measured using a series of traits, specifically leafiness, plant height and tissue chlorophyll and N content, reflects adaptation to edaphic environments which vary in terms of their nutritional properties. The fact that the radiation in Cape Thesium has been accompanied by morphological shifts, which are consistently associated with shifts to different environments, suggests that diversification in Thesium has been adaptive. I therefore propose that edaphic heterogeneity in the CFR has playedUniversity a significant role in driving the morphological and taxonomic diversification of Cape Thesium. Parasitism in Thesium may thus represent a specialized foraging strategy for overcoming deficiencies in available nutrients in the nutrient poor environments of the CFR. iv Table of Contents Plagiarism declaration .............................................................................................................ii Acknowledgements .................................................................................................................iii Abstract ....................................................................................................................................iv Chapter 1 ...................................................................................................................................1 General Introduction................................................................................................................1 Declaration of student contribution to published manuscript.......................................................7 Chapter 2....................................................................................................................................8 Phylogenetics and biogeography of the parasitic genus Thesium L. (Santalaceae), with an emphasis on the Cape of South Africa.....................................................................8 Abstract..................................................................................................................................8 Introduction.............................................................................................................................9 Materials and Methods.........................................................................................................14 Taxon sampling................................................................................................................14 Phylogenetic analyses and molecular dating...................................................................16 Results..................................................................................................................................18 Separate analyses...........................................................................................................19 Combined analyses.........................................................................................................22 Biogeography and dating.................................................................................................24 Discussion............................................................................................................................26 Appendices.............................................................................................................Town ..............32 Chapter 3..................................................................................................................................39 The role of edaphic variation in shaping divergence in carbon acquisition traits in the hemiparasitic genus Thesium L. (Santalaceae) in the Cape Floristic Region...................39 Abstract................................................................................................................................39 Introduction...........................................................................................................................40 Materials and Methods.........................................................................................................Cape 45 Field data collection and species sampling......................................................................45 Plant trait analysis............................................................................................................of 46 Soil analysis.....................................................................................................................47 Habitat specificity.............................................................................................................47 Trait-environment associations........................................................................................48 Pot experiment.................................................................................................................49 Herbarium sampling.........................................................................................................50 Results..................................................................................................................................50 Plant traits........................................................................................................................50