published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

The genus Polyalthiais one of the largest genera in the early-divergent angiosperm family Annonaceae, with ca. 155 currently accepted species. The genus has long been recognised as a morphologically heterogeneous assemblage lacking conspicuous synapomorphies, and is one of the most significant impediments to revisionary and floristic taxonomic research in the family. The polyphyletic status of the genus has been confirmed in several molecular phylogenetic studies, with several other genera (Enicosanthum, Fenerivia, Haplostichanthus, Marsypopetalum, Monoon, Trivalvariaand Woodiellantha)either closely related to or with species formally assigned to Polyalthia. This thesis presents the most comprehensive molecular phylogenetic study of Polyalthiato date, including 44Polyalthiaspecies and 16 species from putatively related genera. The phylogeny was reconstructed using maximum parsimony (MP), maximum likelihood (ML) and Bayesian inference (BI)methods, based on three chloroplast DNA regions (matK, rbcLand trnL-F). The Polyalthia species are shown to segregate into four clades: (I) a clade sister to Miliusa; (II) a clade that includes four Polyalthia species and also Marsypopetalum pallidum, sister to Trivalvaria; (III) a clade that also includes all Enicosanthum and Woodiellantha species sampled, sister to Neo-uvaria; and (IV) a clade that also includes all Haplostichanthus species sampled, sister to Popowia. All four identified Polyalthia clades are located in the tribe Miliuseae. In order to assess the relationships among different Polyalthia clades as well as the relationships among all the genera in Miliuseae, a pilot study on the phylogenetic utility of a wide range of markers was carried out. Based on the result, eight chloroplast markers (matK, rbcL, trnL-F, psbA-trnH, ndhF, ndhF-rpl32, rpl32-trnLand ycf1) were selected and further sequenced for the clade representatives. Although unsuccessful in resolving the Miliuseae, the recognition of three of the four Polyalthia clades as monophyletic genera was confirmed. Diagnostic morphological and anatomical characters were evaluated for clades II–IV, with the emphasis on putative synapomorphies. The morphology of the species not sampled for molecular study was examined in detail and compared against diagnostic characters to determine correct taxonomic placement. Based on the results, five Polyalthia species are transferred to Marsypopetalum. The generic name Monoon is resurrected for the clade that includes Enicosanthum and Woodiellantha, with the transfer of 37 species from Polyalthia s.l., 18 species from Enicosanthum and one Woodiellantha species. The generic name Haplostichanthus is synonymised with Polyalthias.str., with the 11 Haplostichanthus species transferred to Polyalthias.str.. The eight Polyalthia species reported from Fiji were further sampled in a phylogenetic reconstruction based on three markers (matK, rbcLand trnL-F). Three groups were identified, allied with Goniothalamus, Polyalthia Clade I and Meiogyne respectively. The flower of Fenerivia capuronii (Cavaco & Keraudren) R.M.K. Saunders was selected for anatomical studies to examine whether the flange represents a reduced calyx as suggested for F. heteropetala and thus to test a possible homoetic mutation in F. capuronii. The results show that there is no vascular supply in the flange of F. capuronii, and that the putative homeotic change within Feneriviais therefore likely to only occur in F. heteropetala. / published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 298-323).

published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

Goniothalamus is one of the largest genera in the pantropical angiosperm family Annonaceae. It includes c. 130 species of trees, distributed in tropical lowland and submontane forests in tropical Asia, Australia and Melanesia. Previous studies have indicated that Goniothalamus shows a significantly higher diversification rate in comparison to closely related taxa and that its species diversity is the result of a relatively recent radiation. The phylogenetic framework necessary for testing this hypothesis, including the investigation of potential intrinsic and environmental correlates of this putative radiation, and additional biogeographical and evolutionary studies, has not previously been available. Data from nine chloroplast DNA markers (11,214 aligned characters) and 67 ingroup accessions (c. 50% of the species diversity) of Goniothalamus are used for parsimony, maximum likelihood and Bayesian phylogenetic reconstructions. The results confirm the monophyly of Goniothalamus, indicate several strongly supported major subclades, and show that most previously described infrageneric taxa are para- or polyphyletic. Morphological character evolution in Goniothalamus is investigated using ancestral character state reconstructions and phylogenetic analysis of variance. The evolutionary patterns of 19 morphological characters for which a significant phylogenetic signal was identified are discussed in relation to function. Character correlations indicate two main fruit types: small monocarps (average diameter c. 1 cm) with glabrous seeds borne on young growth, which are hypothesized to be predominantly bird-dispersed, and larger (average diameter 1.5 cm) monocarps with hairy seeds borne on older twigs, the trunk or close to the ground, hypothesized to be predominantly mammal dispersed. Synapomorphies of several subclades of the Goniothalamus phylogeny are identified based on the ancestral character reconstructions of 11 categorical characters. Molecular dating is performed using two fossil calibrations, an uncorrelated rates relaxed molecular clock model, and the most comprehensive Annonaceae dataset to date (738 ingroup and 5 outgroup accessions, nine chloroplast markers), with the aim of investigating the historical biogeography of Goniothalamus. Mean divergence time estimates indicate a Goniothalamus crown group age of 23 Ma. Biogeographical analyses infer an ancestral area in western Southeast Asia, two dispersal events from western Southeast Asia to India, and multiple dispersal events from western Southeast Asia eastwards to the Philippines, New Guinea and Australia in the early to late Miocene. Diversification analyses corroborate previous studies which indicated that early Annonaceae diversification was characterized by a low net diversification rate and high relative extinction rate. The results of the present study, however, also indicate that the diversification rate peaked between 9.9 and 0.8 Ma, associated with a low relative extinction rate. Temporally coinciding environmental (tectonic and climatic) factors which may underlie this diversification peak are discussed. In contrast to previous studies, the results do not suggest that the species diversity in Goniothalamus is the result of a rapid, recent radiation. Significant rate shifts are not indicated when using methods that accommodate incomplete taxon sampling. Previously inferred rate shifts are probably artefacts because of inadequate taxon sampling. Significantly high diversification rates are identified in the present study in several small to medium-sized Asian genera such as Polyalthia s.str. and Monoon. / published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy