The period between pollination and fertilization, or the progamic phase, is a critical life history stage in seed plants and innovations in this life history stage are hypothesized to have played an important role in the diversification of flowering plants. Over the course of this dissertation research, I investigated programic phase development in Nymphaeales (water lilies), an ancient angiosperm lineage that diverged from the basalmost or next most basal node of the angiosperm phylogenetic tree and that is represented in the oldest angiosperm fossil record. I used field experiments and microscopy to document pollination biology, breeding system, and reproductive developmental traits in two families of Nymphaeales: Cabombaceae (Brasenia, Cabomba) and Hydatellaceae (Trithuria). Nymphaeales exhibits considerable variation in reproductive traits and true carpel closure, wind-pollination, and a primarily selfing breeding system have arisen independently in the lineage. Pollen tube pathway length, timing of stigma receptivity, and pollen tube growth rates are conspicuous traits that have undergone considerable modification in concert with shifts in pollination biology and breeding system. Post-pollination developmental processes in Nymphaeales appear to experience selective pressures similar to those experienced by more derived angiosperms and to evolve in similar ways. Nymphaeales also exhibits traits, such as accelerated pollen tube growth, callosic pollen tube walls, and the formation of callose plugs, that are almost certainly plesiomorphic in angiosperms and may have facilitated modification of carpel structure and progamic phase ontogenies. The finding that pollen tube traits that underlie developmental flexibility were already in place before the divergence of Nymphaeales supports the hypothesis that innovations in male gametophyte development were instrumental in facilitating early angiosperm diversification.

The Aristolochiaceae are one of the largest angiosperm families, the family has been divided into two subfamilies: Asaroideae, which include Asarum and Saruma, and Aristolochioideae, which includes Thottea sensu lato and Aristolochia sensu lato (Kelly and Gonzales, 2003). Aristolochia sensu lato comprise between 450 and 600 species, distributed throughout the world with centers of diversities in the tropical and subtropical regions (Neinhuis et al., 2005, Wanke et al., 2006a, 2007). However, the extended Mediterranean region including Turkey, the Caucasus and the Near East is likely to be the only diversity hotspot of the genus Aristolochia in the northern hemisphere were up to 60 species and subspecies could be observed (Wanke 2007). Most important contributions to the knowledge of these species were published by Nardi (1984, 1988, 1991, 1993) and Davis & Khan (1961, 1964, 1982), all of these studies were based on morphological characters only. In recent years, with the progress of molecular techniques and in light of the systematic chaos, a detailed study was needed to unravel the evolutionary history prior to a taxonomic revision of this group. The first chapter of my thesis should be regarded as the starting point for more detailed investigation on population level. Preliminary molecular phylogenitic analysis recovered the Mediterranean Aristolochia species as monophyletic (de Groot et al 2006). However, only very few members were included in that study. The latest phylogenetic study by Wanke (2007) dealed with west Mediterranean Aristolochia species and sampled also few members belonging to the east Mediterranean and Caucasian species (3 from Greece, 2 from Georgia and 1 from Turkey). This study reported the Mediterranean Aristolochia species as two molecular and morphologically well supported clades, which were sister to each other. Furthermore, the two closely related species A. sempervirens and A. baetica which have an east west vicariance and are known as Aristolochia sempervirens complex has been recovered as sister group to the remaining west Mediterranean species. A detailed investigation of the evolutionary history of this group is the topic of the second chapter of my thesis (Chapter 2). The Aristolochia sempervirens complex is characterized by an unusual growth form and has a circum Mediterranean distribution. The investigation of these species complex seem to be of great importance to understand speciation and colonization of the Mediterranean by the genus Aristolochia and might shade light in historical evolutionary processes of other plant lineages in the Mediterranean. Furthermore, I test applicability and phylogenetic power of a nuclear single copy gene (nSCG) region to reconstruct well resolved and highly supported gene genealogies as a prerequisite to study evolutionary biology questions in general. Furthermore, a comprehensive overview of leaf epicuticular waxes, hairs and trichomes of 54 species from the old and new world taxa of the genus Aristolochia were investigated using scanning electron microscopy (SEM) to clarify taxonomic status of theses species in contrast to their molecular position. Also this study which is the third chapter of this thesis (Chapter 3), has a strong focus on Mediterranean Aristolochia and tries to provide additional support for molecular findings based on epicuticular waxes and to test them as synapomorphies. Each chapter has its own introduction and abstract resulting in a short general introduction here.

The Aristolochiaceae are one of the largest angiosperm families, the family has been divided into two subfamilies: Asaroideae, which include Asarum and Saruma, and Aristolochioideae, which includes Thottea sensu lato and Aristolochia sensu lato (Kelly and Gonzales, 2003). Aristolochia sensu lato comprise between 450 and 600 species, distributed throughout the world with centers of diversities in the tropical and subtropical regions (Neinhuis et al., 2005, Wanke et al., 2006a, 2007). However, the extended Mediterranean region including Turkey, the Caucasus and the Near East is likely to be the only diversity hotspot of the genus Aristolochia in the northern hemisphere were up to 60 species and subspecies could be observed (Wanke 2007). Most important contributions to the knowledge of these species were published by Nardi (1984, 1988, 1991, 1993) and Davis & Khan (1961, 1964, 1982), all of these studies were based on morphological characters only. In recent years, with the progress of molecular techniques and in light of the systematic chaos, a detailed study was needed to unravel the evolutionary history prior to a taxonomic revision of this group. The first chapter of my thesis should be regarded as the starting point for more detailed investigation on population level. Preliminary molecular phylogenitic analysis recovered the Mediterranean Aristolochia species as monophyletic (de Groot et al 2006). However, only very few members were included in that study. The latest phylogenetic study by Wanke (2007) dealed with west Mediterranean Aristolochia species and sampled also few members belonging to the east Mediterranean and Caucasian species (3 from Greece, 2 from Georgia and 1 from Turkey). This study reported the Mediterranean Aristolochia species as two molecular and morphologically well supported clades, which were sister to each other. Furthermore, the two closely related species A. sempervirens and A. baetica which have an east west vicariance and are known as Aristolochia sempervirens complex has been recovered as sister group to the remaining west Mediterranean species. A detailed investigation of the evolutionary history of this group is the topic of the second chapter of my thesis (Chapter 2). The Aristolochia sempervirens complex is characterized by an unusual growth form and has a circum Mediterranean distribution. The investigation of these species complex seem to be of great importance to understand speciation and colonization of the Mediterranean by the genus Aristolochia and might shade light in historical evolutionary processes of other plant lineages in the Mediterranean. Furthermore, I test applicability and phylogenetic power of a nuclear single copy gene (nSCG) region to reconstruct well resolved and highly supported gene genealogies as a prerequisite to study evolutionary biology questions in general. Furthermore, a comprehensive overview of leaf epicuticular waxes, hairs and trichomes of 54 species from the old and new world taxa of the genus Aristolochia were investigated using scanning electron microscopy (SEM) to clarify taxonomic status of theses species in contrast to their molecular position. Also this study which is the third chapter of this thesis (Chapter 3), has a strong focus on Mediterranean Aristolochia and tries to provide additional support for molecular findings based on epicuticular waxes and to test them as synapomorphies. Each chapter has its own introduction and abstract resulting in a short general introduction here.

En raison de sa remarquable diversité végétale, de son taux d’endémisme, parmi les plus élevés au niveau mondial (79%) et de son extrême vulnérabilité, la Nouvelle-Calédonie est un des premiers hotspots de la biodiversité mondiale. L’une des remarquables originalités de la flore Calédonienne repose sur la présence de nombreux taxa reconnus, en raison de leurs positions phylogénétiques, comme appartenant aux lignées les plus anciennes des plantes à fleurs. Ces lignées d’Angiospermes « reliques » ont une valeur scientifique et patrimoniale importante, puisqu’elles sont de véritables fenêtres sur le passé. A travers l’étude des traits foliaires, de l’anatomie du bois (e.g. type d’éléments conducteurs, perforations, diamètre et longueur des vaisseaux), de l’architecture (e.g. sympoldialité vs monopodialité, phénomène de réitération, rythmicité de croissance) et de la biomécanique des axes, nous chercherons à caractériser les formes et fonctions de ces taxons. Ce projet de thèse vise à examiner les déterminants structurels et fonctionnels de la répartition spatiale actuelle des Angiospermes basales (grade ANITA + Magnoliidae) en Nouvelle-Calédonie. Dans cette perspective nous chercherons à comprendre quels sont les facteurs qui ont conduit au confinement de certains taxons à des habitats restreints ou au contraire à leur dispersion dans des milieux contrastés. Un premier volet du projet en cours, a pour objectif de caractériser la dynamique de croissance d’Amborella trichopoda et sa plasticité architecturale sous différents régimes lumineux. Certains traits écologiques de ces espèces d’Angiospermes de divergence précoce, s’ils n’ont pas contribué à la radiation des plantes à fleurs actuelles, ont pu permettre son enracinement écologique au sein de la flore du Mésozoïque et fournir un répertoire développemental pour l’explosion subséquente de leur diversité. L’identification et l’étude de ces caractères sont donc déterminantes pour la compréhension de l’évolution structurelle et fonctionnelle des plantes à fleurs. / New Caledonia (NC) is one of the main biodiversity hotspots (Myers 1988), this is because of its remarkable plant diversity, its endemism rates, among the highest in the world (79%), and because of the vulnerability of its flora. One of the main originalities of New Caledonia flora is based on the presence of a large number of taxa recognized, due to their phylogenetical positions, as the most ancient extant representatives of angiosperms. For a long time, New Caledonia has been considered as an early upset fragment of the Gondwana (Pelletier 2006) that suffered an interrupted history of isolation which conferred the evolutionary particularities that we observe today. However, recent evidences show that NC has derived from the Australian land during the late Mesozoic (~80 Mya), the island was then submerged during the first half of the Cenozoic (Pelletier 2006) and a reemergence of the island seems to have occurred ~37 Mya (Cluzel et al. 1998). After the reappearance of the island above the sea level, several events of recolonisation occurred and they wrought the biodiversity that we observe nowadays (Pillon 2012). NC presents humid forests which are unique relics; under the influence of climate changes, these forests have virtually disappeared from other regions of the globe (Morat et al. 1986). The lineages of “relictual” angiosperms, mainly subservient to these humid forests, have a great scientific and patrimony value, as they can be considered as genuine windows on the past. These taxa are susceptible to contain primitive characters which have either disappeared in most of the existing flowering plants, or that are still shared by a narrow number of them. The identification and the study of these characters are therefore determinants for the comprehension of angiosperms evolution. Some ecological features of these panchronic species, may have either contributed to the huge radiation of extant angiosperms, or they may have contributed to the ecological settling of angiosperms within the Mesozoic flora, providing them with a developmental repertoire for the subsequent explosion of their diversity. This PhD project aims to study the ecological, anatomical and functional diversity of basal angiosperms and it seeks to analyze the evolutionary patterns of these structural and functional features. We will consider here as “basal” angiosperms a great group of flowering plants that has diverged before the monocot and eudicot node. This group is conformed by the ANITA grade, formed by Amborella (a single species endemic to NC), Nymphaeales (waterlilies and other herbaceous aquatic plants) and Austrobaileyales (aromatic woody plants). The Magnoliid subclass, a clade of flowering of early divergence, which contains plants considered as paleodicots by Cronquist (1988), will be also included in the analysis of the « basal » taxa. More recently, the Magnoliids have been redefined as a clade comprising Chloranthales, Canellales, Laurales, Magnoliales, et Piperales (APG III, 2009). In a second part of the project, a fieldtrip to Mexico will be held in order to include speces belonging to the Chloranthaceae and Schisandraceae, as well as Cabombaceae et Nymphaeaceae, by this means, we will incorporate species belonging to all the orders of the “basal” angiosperms, reinforcing the comparative analysis. This research work will lean on the recent publications of the phylogenetic relations within basal angiosperms...