Introduction Chapter 1

CHAPTER 1 INTRODUCTION 1.1 General introduction and taxonomic complexities in Fagraea sensu lato: three distinct subgeneric groups; variance in species delimiting concepts The genus Fagraea Thunberg is pantropical, with a distribution from Sri Lanka and India, through tropical South East Asia, reaching as far east to Polynesia (Struwe et al. 2002). The genus is centered in Malesia, where of over 70 species described (Struwe et al. 2002), around 50 species are distributed within Peninsular Malaysia and Borneo (Leenhouts 1962; Wong & Sugau 1996). Species of Fagraea have a variety of life forms. They are tall canopy trees, smaller understorey trees reaching only a few meters tall, or are epiphytes and hemi-epiphytes. They occur from sea level to about 3000 m in very moist montane conditions, mostly in forest gaps, forest edges, rocky outcrops, along stream beds in wet tropical forests but less commonly in mesic forests, mangrove swamps and savannas (Motley 2004). With a large diversity in habit and form, Fagraea have species that are both conspicuous and ecologically important in natural landscapes. The widespread F. fragrans is a common pioneer on sandy sites, a frequent secondary forest species in the lowlands, and can persist in mature forest. In Peninsular Malaysia, F. racemosa is also a common secondary forest species and the large-leaved F. auriculata with long-tubed flowers is often conspicuous in coastal sandy sites and on quartz ridges in the lowlands. Throughout the lowland and lower montane forests of Peninsular Malaysia and Borneo, the frequent 1 presence of Fagraea epiphytes or hemi-epiphytes is detected by fallen corollas on the ground at different times during the year. Many species are useful (Motley 2004). Fagraea is currently placed in the family Gentianaceae within tribe Potalieae and subtribe Potaliinae (Struwe et al. 2002). In the past, Fagraea have been placed within the Loganiaceae (e.g., Leeuwenberg & Leenhouts 1980; Leenhouts 1962) but this classification is now controversial. Subsequent analysis of morphological data (Struwe et al. 1994; Struwe & Albert 1997) and molecular characteristics (Struwe et al. 2002; Downie & Palmer 1992; Olmstead et al. 1993) have demonstrated that Fagraea and its tribe Potalieae are better placed in the Gentianaceae. Some phytochemical evidence (Jensen 1992; Jensen & Schripsema 2002) also supports the placement of Fagraea in the Gentianaceae. The only two clear morphological (non-synapomorphous) characters that make the tribe Potaliinae aberrant in Gentianaceae are the occurrence of fleshy berries and occasional large tree habit in some taxa (Molina & Struwe 2009). Other members of the Gentianaceae have dry and capsular fruits and relatively smaller size (Struwe et al. 2002). Fagraea is closely related to Anthocleista Afzel. ex R. Br. and Potalia Aublet within the Potaliinae (Struwe et al. 2002). Whereas Fagraea is a large Indo-Pacific genus, Potalia is found in the Central and South American region with nine recorded species and Anthocleista is only found in tropical Africa and Madagascar with 14 known species (Struwe et al. 2002). Molecular analyses have consistently shown that the three genera viz., Anthocleista, Fagraea and Potalia form a monophyletic group that justifies inclusion in the same subtribe within Gentianaceae (Struwe et al. 2002; Molina & Struwe 2009). Within Fagraea, three subgeneric groups have been recognized, considered as the sections Cyrtophyllum, Fagraea and Racemosae (Leenhouts 1962). This sectional 2 classification was adopted by Wong & Sugau (1996), who delimited the sections by inflorescence form and branching, seed form, the nature of fruit epidermis, axillary scale characters and stigma form. In their review for Borneo, Wong & Sugau (1996) enumerated 42 species, including 20 that they newly described. This was a big contrast to the previous work by Leenhouts (1962, 1984) for Malesia, where he only enumerated 15 species for Borneo. The species concepts of Leenhouts were considered too broad by Conn & Brown (1993) and Wong & Sugau (1996). An example stated by Wong & Sugau (1996) is that Leenhouts (1962) had only one species accepted in the whole section Racemosae for Malesia, having reduced many previously described species to synonymy. Wong & Sugau (1996) found many of such taxa morphologically distinct and possible to key out using both vegetative and flower and fruit characters, and resurrected such names from synonymy. 1.2 Scope of work and objectives The bizarre contrast between the results obtained by Leenhouts (1962) and Wong & Sugau (1996), the demonstration of what appears to be likely impractical species concepts in Leenhouts (1962) by both Conn & Brown (1993) and Wong & Sugau (1996), and the lack of any recent detailed reviews for Malesia other than Borneo, precipitated the present inquiry. Moreover, herbarium holdings of Fagraea material would have increased since the accounts by Leenhouts (1962) and Kochummen (1973), the latter being the most recent account for Peninsular Malaysia. At the fundamental level, the distinctness of the subgeneric groups recognized as Fagraea sections Cyrtophyllum, Fagraea and Racemosae require further consideration. 3 This is in view of somewhat conspicuous characters distinguishing them, as summarised by Wong & Sugau (1996), and very preliminary possibilities for generic distinction suggested by limited molecular evidence discussed by Struwe & Albert (1997). This problem is investigated using a molecular analysis of as many taxa as possible from the Malay Peninsula and Borneo, and augmented by molecular results for other taxa in the same subtribe and tribe from other regions. Parallel to this, a revision of the taxa constituting Fagraea sensu lato in the Peninsular Malaysia is conducted. This necessarily draws on herbarium materials and new field studies. Besides allowing a review of species morphological and ecological distinctions, this work would also re-examine the extents of morphological distinction among the so-called sections. Finally, the merits and intricacies of classifying the several morphologically distinct groups of species within Fagraea sensu lato as either sections or distinct genera will be discussed. From this, recommendations would be made for an appropriate classification of the group, including any necessary taxonomic adjustments. 4 CHAPTER 2 LITERATURE REVIEW 2.1 Taxonomic History of Fagraea 2.1.1 Relevant taxonomic documentation The genus Fagraea was originally described by Thunberg in 1782 based on the type species F. ceilanica collected from Galle, Sri Lanka. Since then, single to several species have been added piecemeal by Jack (1822), Roxburgh (1824), Blume (1826, 1850), Clarke (1883), Curtis (1894), Ridley (1908, 1918), Merrill (1917), Henderson (1933), Craib & Kerr (1951), Leenhouts (1984), Kochummen (1973) and Wong et al. (1987). On the other hand, a few floristic accounts have attempted summaries of the genus for the Malay Peninsula (King & Gamble 1904, Ridley 1923) and the Malay Archipelago in general (Cammerloher 1923, Leenhouts 1962). More recently, Wong & Sugau (1996) revised the genus for Borneo with remarks on related species elsewhere, and Conn & Brown (1993) reviewed the F. gracilipes complex in east Malaysia and Australia. 2.1.2 From Loganiaceae to Gentianaceae: familial classification and taxonomic position of Fagraea and the Potalieae The genus Fagraea Thunb. is currently placed within the Gentianaceae, as tribe Potalieae, subtribe Potaliinae, together with two other genera, Potalia Aublet and Anthocleista Afzel. ex R. Br. (Struwe et al. 2002). In the past, however, the placement of Fagraea has been controversial. In the early classification by Jussieu (1789), Fagraea was placed in the Apocynaceae, although other subsequently published works have mostly placed it in the Loganiaceae (e.g., Blume 1826, Ridley 1923, Leenhouts 1962 and Wong & Sugau 1996). Leenhouts (1962) and Leeuwenberg & Leenhouts (1980) used the tribe Potalieae for these three genera, but under the family Loganiaceae. Wood anatomical 5 studies of Anthocleista, Fagraea and Potalia were considered by Mennega (1980) and Jensen & Smets (1998) as providing support for the taxonomic placement of Fagraea within the Loganiaceae. Anthocleista, Fagraea and Potalia have also been treated as a separate family, Potaliaceae, by von Martius (1826–1827) and Hutchinson (1973). The present classification by Struwe (2002) of Fagraea and the two allied genera (Anthocleista and Potalia) within Gentianaceae is not a novel idea as this affinity has been suggested in the past. Earlier works such as by Jussieu (1791), had considered the Fagraea-allied genus Potalia to be a gentian. Bureau (1856) had formally transferred the tribe Potalieae (as "tribu des Fagraeacées") from Loganiaceae to Gentianaceae. Bentham (1857) and Gray (1859) also suggested the relationship of the genera Anthocleista, Fagraea and Potalia with other neotropical woody gentians and remarked on the similarity between Fagraea and Lisianthius (a genus within the same tribe Potalieae in the current classification) (see Table 1). Gray (1859) recognised that Fagraea berteriana had the bilamellate stigma of Lisianthius and Bentham (1857) noted that the only major difference between these taxa was the more developed placentas of Fagraea. Fosberg & Sachet (1974, 1980) also suggested including the Potalieae in Gentianaceae, although Leeuwenberg & Leenhouts (1980) did not agree (they however, did not provide any evidence to the contrary). Later, Taktajan

Load more