CHAPTER 1 GENERAL INTRODUCTION This Thesis
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CHAPTER 1 GENERAL INTRODUCTION This thesis contains the result of morphological studies of Thai Artabotrys, molecular systematic studies of the genus Artabotrys and pollen morphology of the tribe Unoneae including genus Artabotrys are presented. Each Chapter includes its own introduction. Annonaceae and Artabotrys classification will be introduced briefly and the research objectives will be presented. An outline of the thesis concludes this introduction. FAMILY ANNONACEAE The family Annonaceae is a member of Magnoliales and basally positioned within the angiosperms together with Canellales, Laurales, Piperales, Chloranthales, and monocots (Soltis et al., 2000; APG II, 2003). Sister to Annonaceae are Eupomatiaceae (Qiu et al., 2000; Fig. 1.1) which were previously included as a subfamily within Annonaceae and have always been considered closely related based on morphological characters (Takhtajan, 1980; Cronquist, 1988; Morawetz, 1988; Thorne, 2000). The Family has a predominantly pantropical distribution (Figure 1.2) and consists of approximately 130 genera and 2500 species (Chatrou et al., 2004). They show a high diversity of generic and species in Asia, Australia and the Pacific (Mols, 2004). Only Xylopia can be found in three regions distribution. Artabotrys, Polyalthia, Uvaria and Frisodielsia occurr in both Africa and Asia. Although the distribution of most genera is limited to one continent. So far, genera with a 2 Neotropical/ African distribution have been focused on. Artabotrys will be the first genus with an African/ Asian distribution to be studied in more detail. Figure 1.1 Schematic representation the position of family Annonaceae within the order Magnoliales (www.mobot.org/MOBOT/research/APweb/) CLASSIFICATION OF ARTABOTRYS All previous classifications of Artabotrys were based on morphological characters. There are summarized below. Hooker (1855) divided the family into six tribes: Annoneae, Uvarieae, Milliuseae, Mitrephoreae, Xylopieae and Guatterieae, based on flower characters alone. According to this classification, the genus Artabotrys is considered as a member of tribe Guatterieae. In 1873, these authors recognized only five tribes with 3 the Annoneae included in the Xylopieae and the tribe Guatterieae was renamed Unoneae. Ridley (1922) divided the Annonaceae into six tribes. Sinclair (1955) included Artabotrys in the subfamily Annonoideae tribe Unoneae together with Cyathocalyx, Desmos, Monocarpia, Oncodostigma, Meiogyne, Polyalthia, Cananga, Mezzetia and Disepalum. He based this on floral characters, in which petals are valvate, spreading above; the three inner petals separate at the base but fall as one piece, and the fact that they are woody climbers. Hutchinson (1923, 1964) used the same characters for all Annonaceae genera resulting in an artificial classification. He recognized two subfamilies Annonoideae and Monodoroideae. The Annonoideae were divided into three tribes; Uvarieae, Miliuseae and Unoneae, in which the petals are valvate, equal in size, or the inner are smaller and frequently of a different shape and as a rule more or less clawed and remaining connivent and closely adpressed over the stamens and carpels. He arranged the genera of this tribe into two subtribes; Annonineae and Xylopiineae. Within the Xylopiineae he had three groups, A, B, and C based on the number of petals. Artabotrys was placed in Group A (Hexapetalae). These groups are now considered to be artificial. Fries (1959) divided the tribe Unoneae (valvate petals) into 14 groups based on the position of the inflorescence, the number and position of the ovules and fruit types. Walker (1971) introduced a major change to the general classification within the family. He used pollen morphology to classify Annonaceae into 3 subfamilies, the 4 Malmea, Fusaea, and Annona subfamilies, The genus Artabotrys was placed in the Uvaria tribe which was defined by having solitary, globose pollen grains which are apolar, radiosymmetric, inaperturate medium to large size with well - developed to reduced columellae and often with a verrucate exine. Van Heusden (1992) partly re-evaluated floral characters. New characters were used and the significance of more traditional characters to the classification of the genera was reinterpreted. Nineteen groups were recognized and Artabotrys was placed into the Friesodielsia group together with Cyathocalyx, Dasoclema, Dasymaschalon, Desmos, Fissistigma, Friesodielsia, Mitrella, Monocarpia, Pyramidanthe, Schefferomitra and Sphaerocoryne. Keßler (1993) placed Artabotrys within the Xylopia group (Xylopia, Anaxgorea, Pseudo-artabotrys, Cyathocalyx, Drepananthus and Diclinanona) because of its valvate sepals and petals, spoon-shaped petals with a concave base which is coherent around the reproductive organs. Figure 1.2 Distribution maps of Annonaceae in pantropical region (www.mobot.org/MOBOT/research/APweb/) 5 THE GENUS ARTABOTRYS Artabotrys is one of the species- rich genera in Annonaceae which distributed in tropical Africa and Asia. The majority of the species can be found in the two latter areas. The genus Artabotrys was first described by Ker- Gawler in 1820 (Nurainas, 2004) with the type species A. odoratissimus. The generic name was suggested by R. Brown because its peduncle has a hook. Previously A. odoratissimus had been placed in Unona, Annona or Uvaria. However, it differs from Unona in petal shape, seed number, seed position and peduncle characters; from Annona in fruit and petal characters and from Uvaria in peduncle shape, petal and fruit characters. Bhandari (1964) concluded A. odoratissimus was a synonym for A. hexapetalus (L. f.) Bhandari (Nurainas, 2004).This genus is easily recognized by the flattened hooks at the base of peduncle and its climbing habit. There are three sepals which are valvate, free or united at the base. The six petals are valvate, in two whorls of three, usually subequal, spoon- shaped, connivent around the reproductive organs. Figure 1.3 Distribution maps of Artabotrys in tropical Asia and Africa (www.mobot.org/MOBOT/research/APweb/) 6 This study focuses on the Thai Artabotrys, which is unclear in number of species, so are very difficult to classify. The complement morphological data, pollen morphology and molecular sequence data of the Artabotrys will disclose the relationships among the species and their evolution. RESEARCH OBJECTIVES The major challenge in the taxonomy of Artabotrys has been difficulty in finding good morphological characters to distinguish the species well. More than 100 published species names are listed in the International Plant Index (IPNI, 2008), apparently the most recent database for Artabotrys on a worldwide basis. Because a world monograph and checklist are lacking, species concepts vary considerably among regional floras. The ultimate research objectives addressed in this thesis are: 1.1 To study the taxonomy of the genus Artabotrys in Thailand. 1.2 To study the palynology of the tribe Unoneae in Thailand. 1.3 To study the molecular relationships of species within the genus Artabotrys using DNA sequences data. OUTLINE OF THE THESIS The aim of Chapter 2 is to test monophyly of the genus Artabotrys by phylogenetic analysis of trnL- F, ndhF, psbA- trnH and AP3 DNA sequence data. Comparisons the position of African and Asian species within the genus Artabotrys. Chapter 3 the aim is to study the taxonomic value of pollen morphology in the tribe Unoneae in Thailand. The five genera (Artabotrys, Cananga, Desmos, Cyathocalyx and Polyalthia) in the framework of this thesis are treated. 7 In Chapter 4 a taxonomic study of the genus Artabotrys in Thailand is presented. All 14 recognized species are treated, identification key, descriptions, distribution map and colors photographs are provided. In Chapter 5, conclusions are given. .