Morphological homogeneity, phylogenetic heterogeneity and systematic complexity in species-rich groups: a case study of floral evolution in Myrteae (Myrtaceae) Thais Nogales da Costa Vasconcelos University College London (‘UCL’) A thesis submitted as part of the requirements for a PhD degree in Systematics and Evolutionary Biology Research Department of Genetics, Evolution and Environment - University College London Comparative Plant and Fungal Biology Department – Royal Botanic Gardens, Kew 1 ‘ I, Thais Nogales da Costa Vasconcelos, confirm that the work presented in this thesis is my own. Where information has been derived from other sources, I confirm that this has been indicated in the thesis.' __________________________ ABSTRACT Myrteae is the most diverse tribe in the species-rich angiosperm family Myrtaceae. Myrteae species play a critical ecological role in tropical forests and savannas, biomes with some of the highest biodiversity on earth. Hence there is a growing interest in its use as a model for evolutionary, ecological and conservation studies. However, morphologically homogeneous reproductive structures cause taxonomic instability and jeopardize modelling and conservation initiatives. This study demonstrates how evolutionary patterns are underpinned by floral traits in Myrteae. Aims are approached using combined phylogenetic and morphological analyses in two work packages (WP): WP1 increases understanding of systematics and floral evolution in Myrteae based on multiloci molecular matrices for a near complete generic sample. The framework is used to interpret biogeography, diversification and over-arching patterns of floral morphology and development; data are reciprocally combined to illuminate those processes. WP2 presents four case studies using floral development and multidimensional trait analysis to address questions related to systematic complexity, phylogenetic heterogeneity and theoretical cladistics concepts, such as evolution of homoplastic traits. Results harness Myrteae as a model group to address relevant questions in plant evolution and systematics; the applicability of this approach to similar questions in other diverse tropical angiosperm groups is discussed. Key words: diversification; macro-evolution; Myrtaceae; phenotypic evolution; phylogenetics; systematics. 2 This thesis is dedicated to the kindness of countless people . Thanks! 3 “The biologists who enter this field must resign themselves to the fact that they can never achieve certainty. Their end point must always be a judgement as to which several hypothesis appears to be most plausible on the basis of presently available factors.” G.L. Stebbins (“Flowering Plants: evolution above the species level”; 1974, p.viii) 4 Table of Contents Notes .......................................................................................................................................15 Introduction: An overview of Myrteae ........ .................................................. ......................16 I.1 What is Myrtaceae? ............................ ..... ................... .............................. ......................16 I.2 What is Myrteae? ...................................... .........................................................................17 I.3 Brief history of Myrteae systematics ......... .........................................................................17 I.4 Morphological vs. phylogenetic heterogeneity ....................................................................19 I.5 Thesis objectives ....................................... .........................................................................20 Work Package I – Systematics and flower evolution of Myrteae ............................................22 CHAPTER 1: Myrteae phylogeny, calibration, biogeography and diversification patterns: increased understanding in the most species rich tribe of Myrtaceae ............................23 INTRODUCTION ............................................ .........................................................................24 1.1 Myrteae systematics and diversity ........... .........................................................................24 1.2 Myrteae global geographic distribution .... .........................................................................26 1.3 Study aims ............................................... .........................................................................26 MATERIALS AND METHODS ....................... .........................................................................27 1.4 Taxonomic sampling ................................ .........................................................................27 1.5 Extraction and sequencing ....................... .........................................................................27 1.6 Phylogenetic analysis............................... .........................................................................28 1.7 Fossil calibration and dating .................... .........................................................................28 1.8 Historical biogeography inference ............ .........................................................................29 1.9 Diversification rates analysis .................... .........................................................................31 RESULTS ....................................................... .........................................................................32 1.10 Phylogenetic tree analysis - Grouping and Main lineages ...............................................32 1.11 The Australasian group .......................... .........................................................................32 1.12 The Myrtus group ................................... .........................................................................34 1.13 Main Neotropical lineage ....................... .........................................................................35 1.14 Ungrouped genera: Myrtastrum and Amomyrtus .............................................................35 1.15 Dating inference ..................................... .........................................................................36 1.16 Biogeographical patterns ....................... .........................................................................37 1.17 Diversification rate shifts ........................ .........................................................................40 DISCUSSION ................................................. .........................................................................41 1.18 Systematic implications .......................... .........................................................................41 1.19 Comparative dating analysis .................. .........................................................................43 1.20 Biogeographical inference ..................... .........................................................................44 1.21 Changes in diversification rates, key innovations and mega-diverse genera ..................51 CONCLUSION ............................................... .........................................................................52 APPENDIX ..................................................... .........................................................................53 CHAPTER 2: Systematic and evolutionary implications of stamen posture in Myrteae (Myrtaceae) ................................................... .........................................................................76 5 INTRODUCTION ........................................... ......................................................................... 77 2.1 Myrteae taxonomic complexity and absence of diagnostic characters ............................. 77 MATERIALS AND METHODS ....................... ......................................................................... 79 2.2 Sampling .................................................. ......................................................................... 79 2.3 Herbarium material .................................. ......................................................................... 79 2.4 SEM analyses .......................................... ......................................................................... 79 2.5 Anthesis type observation ....................... ......................................................................... 80 RESULTS ...................................................... ......................................................................... 80 2.6 Stamen posture ....................................... ......................................................................... 80 2.7 Anthesis type ........................................... ......................................................................... 84 DISCUSSION ................................................ ......................................................................... 85 2.8 Systematic implications of stamen posture and anthesis type in myrteae ........................ 85 2.9 Relationship between stamen posture and hypanthium extension ................................... 88 2.10 Evolutionary implications of hypanthial extension, stamen posture in the bud and floral ecology ....................................................................... ........................................................................