En vue de l’obt ention du DOCTORAT DE L’UNIVERSITÉ DE TOULOUSE Délivré par : Université Toulouse 3 Paul Sabatier (UT3 Paul Sabatier) Discipline ou spécialité : Ecologie, Biodiversité et Evolution Présentée et soutenue par : Joeri STRIJK le : 12 / 02 / 2010 Titre : Species diversification and differentiation in the Madagascar and Indian Ocean Islands Biodiversity Hotspot JURY Jérôme CHAVE, Directeur de Recherches CNRS Toulouse Emmanuel DOUZERY, Professeur à l'Université de Montpellier II Porter LOWRY II, Curator Missouri Botanical Garden Frédéric MEDAIL, Professeur à l'Université Paul Cezanne Aix-Marseille Christophe THEBAUD, Professeur à l'Université Paul Sabatier Ecole doctorale : Sciences Ecologiques, Vétérinaires, Agronomiques et Bioingénieries (SEVAB) Unité de recherche : UMR 5174 CNRS-UPS Evolution & Diversité Biologique Directeur(s) de Thèse : Christophe THEBAUD Rapporteurs : Emmanuel DOUZERY, Professeur à l'Université de Montpellier II Porter LOWRY II, Curator Missouri Botanical Garden Contents. CONTENTS CHAPTER 1. General Introduction 2 PART I: ASTERACEAE CHAPTER 2. Multiple evolutionary radiations and phenotypic convergence in polyphyletic Indian Ocean Daisy Trees (Psiadia, Asteraceae) (in preparation for BMC Evolutionary Biology) 14 CHAPTER 3. Taxonomic rearrangements within Indian Ocean Daisy Trees (Psiadia, Asteraceae) and the resurrection of Frappieria (in preparation for Taxon) 34 PART II: MYRSINACEAE CHAPTER 4. Phylogenetics of the Mascarene endemic genus Badula relative to its Madagascan ally Oncostemum (Myrsinaceae) (accepted in Botanical Journal of the Linnean Society) 43 CHAPTER 5. Timing and tempo of evolutionary diversification in Myrsinaceae: Badula and Oncostemum in the Indian Ocean Island Biodiversity Hotspot (in preparation for BMC Evolutionary Biology) 54 PART III: MONIMIACEAE CHAPTER 6. Biogeography of the Monimiaceae (Laurales): a role for East Gondwana and long distance dispersal, but not West Gondwana (accepted in Journal of Biogeography) 72 CHAPTER 7 General Discussion 86 REFERENCES 91 i Contents. APPENDICES 115 ACKNOWLEDGEMENTS 134 ABSTRACT (ENGLISH) ABSTRACT (FRENCH) ii Chapter 1. General Introduction GENERAL INTRODUCTION. 1 Chapter 1. General Introduction CHAPTER 1. GENERAL INTRODUCTION 1.1 Hotspots of Biodiversity Biodiversity Hotspot: A region containing at least 1500 species of vascular plants as endemics (or >0.5% of the world’s total), and that has less than 30% of its primary vegetation remaining intact (…) (extent of historical habitat cover) (Myers et al., 2000) The interconnectedness and urgency of environmental problems faced across the world today (Dirzo and Raven 2003) demands solutions that are financially sound, the impacts of which can be measured quantatively and that are effective at tackling a range of problems simultaneously and effectively (e.g. conservation, protection of ecosystem services, poverty and debt relief) (Novacek and Cleland 2001). The scale of problems faced and the scarcity of resources to address all these issues individually have led to the formulation of several strategies to optimize the “number of species saved per dollar invested”, the most important of which is the ‘Biodiversity Hotspots’ concept (Myers 1988, 1990; Myers et al. 2000). Since the initial formulation of the Hotspots-concept and the adoption of it by the world’s major conservation and funding bodies (Conservation International, World Bank, Global Environment Facility), public awareness and scientific interest in the global state of our planet’s biodiversity has increased tremendously (Mittermeier et al. 2004). The Hotspots-concept has been used to identify twenty-five areas (Mittermeier et al. 1999; Myers et al. 2000), with an additional nine recently added to the list (Mittermeier et al. 2004). Contained within these 34 regions with a combined global land-surface area of 2.3%, these areas are home to over 150000 species of plants (half the world’s total) occurring as single-hotspot endemics. Furthermore, more than 40% of all known vertebrates occur in these regions. In addition to the Hotspots-concept that has been further developed by Conservation International (2004, 2007), the Wilderness Areas (Mittermeier et al. 1998) Mittermeier et al., 2002, 2003), the Endemic Bird Areas (Birdlife International) (Statersfield et al. 1998) and the WWF Global 200 Ecoregions (Olson and Dinerstein 2002) also recognise regions of outstanding biological interest. These concepts are in close agreement and address aspects of biodiversity and conservation at different geographic and biological scales (Harris et al. 2005). In recent years, the hotspot-concept has faced criticism for a variety of reasons (Brummitt and Lughadha 2003; Kareiva and Marvier 2003; Possingham and Wilson 2005). Although some of the critics raise justified issues (e.g. incomplete coverage, no ecosystem services, no inclusion of Phylogenetic Diversity), other authors propose measures and sets of rules to inform conservation measures that are simply not realistic in today’s world (Myers and Mittermeier 2003). Regardless of the criticism aimed at the hotspots-concept and its inherent shortcomings, over the past decade it has established itself as the dominant paradigm for global conservation strategy used by funding bodies, governments and the scientific community. With data on species accounts within hotspots incomplete, their evolutionary relationships far from understood and our knowledge of the origins and causes for the existence of these hyper-diverse regions still in its infancy, conservationists and 2 Chapter 1. General Introduction policymakers face a daunting task: making the best possible informed choice on where to invest limited resources available, inevitably leaving other areas and species without (or with less) protection (Novacek and Cleland 2001). Short of an unprecedented shift in our behaviour as a species, and given the threats and rates of climate change, habitat alteration and species loss, it is highly unlikely that we will be able to enact enough safeguards to preserve all biodiversity present on our world at this stage (Jenkins 2003). In that sense, the Hotspots-concept remains the most practical and viable starting point to approach to the Global Biodiversity Crisis, although there are indications that at smaller scales a modified strategy may be more effective for conservation planning (Reid 1998; Harris et al. 2005). This thesis is part of a larger project (HOTSPOTS: Understanding and Conserving the Earth’s Biodiversity Hotspots) funded by the Marie Curie Foundation of the European Union and coordinated by the Royal Botanical Gardens Kew (http://www.kew.org/hotspots). The project is aimed at increasing our understanding of the evolutionary and ecological dynamics in biodiversity hotspots. More specifically, it consists of nine doctoral research projects addressing specific questions in the fields of evolution, ecology and conservation across a range of biodiversity hotspots. The focus of this thesis is on patterns of plant diversification and differentiation in the Madagascar and Indian Ocean Islands biodiversity hotspot. This region is particularly suited to address questions related to the “how and why” of species richness as islands, and in particular those created by volcanic hotspots provide us with replicated model systems in which to test theories and models to understand the pathways by which ecology, evolutionary change and biogeography shape the process of species diversification (Paulay 1994; Whittaker and Fernández-Palacios 2007). 1.2 The Madagascar and the Indian Ocean Islands Biodiversity Hotspot As a textbook example of species evolution in isolation, the Madagascar and Indian Ocean Islands (MIOI) Biodiversity Hotspot (Figure 1.1) lines the eastern coast of Africa, consisting solely of islands which, taking into account endemicity at a range of taxonomic levels, can be considered as the world’s single highest-priority hotspot (Mittermeier et al. 2004). Estimates for plant species occurring on Madagascar range from 10000-14000, with endemism levels reaching more than 90% (Goodman and Benstead 2003; Phillipson et al. 2006). The surrounding archipelagos host a surprising number of endemic species, given their relatively small contribution in terms of terrestrial surface area. For example, the Mascarene Archipelago with an area less than 1% of Madagascar area is inhabited by 960 species, one tenth of the total number occurring in Madagascar, 72% of which are restricted to the archipelago (Page and d'Argent 1997; Boullet 2006). The geological origins of the elements that make up the hotspot are quite diverse, and play an important part in providing a range of substrates. Madagascar, the world’s fourth largest island, and the microcontinental granitic fragments of the Seychelles are part of the former super-continent of Gondwana and became isolated during it’s break-up some ~65 and ~135 Mya (McLoughlin 2001; Collier et al. 2008). Roughly two-thirds of the Seychelles islands (74) are of coralline origin and were formed some 3 Chapter 1. General Introduction Figure 1.1 The Madagascar and Indian Ocean Islands Biodiversity Hotspot. Colours show altitudinal range (lowlands - dark; upland - light). 125 Mya during the last major reef building period (Bijoux et al. 2005). Also included in the hotspot are the Îles Éparses, a collection of four small coral islands and one atoll surrounding Madagascar. Finally, two archipelagos of volcanic origin on either side of Madagascar are also part of the hotspot: