Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 243-260). Also available in print.

Thesis (Ph. D.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 465-486).

Thesis (Ph. D.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

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

published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

　　　The Annonaceae is a large, early-divergent family of angiosperms. Although the majority is pollinated by small beetles, there is a great diversity of floral morphologies. Evolutionary shifts of pollination mechanisms have occasionally been reported in disparate lineages including shifts to pollination by large beetles, flies, thrips, bees and cockroaches. It was previously hypothesized that floral morphological changes in different lineages are adaptive and correspond to evolutionary shifts of pollination mechanisms. This hypothesis is tested here by comparing selected species that have substantial morphological differences with their close relatives. 　Comprehensive studies of the floral biology of four Annonaceae species, Dasymaschalon trichophorum, Desmos chinensis, Pseuduvaria mulgraveana and Uvaria cordata, are presented. All are beetle-pollinated. Dasymaschalon trichophorum, D. chinensis and U. cordata were inferred to be self-compatible based on inter-simple sequence repeat marker data as there was evidence of significant gene flow and a low level of genetic differentiation between populations. This was corroborated for D. chinensis and U. cordata by experimental controlled pollination tests for geitonogamy, in which both were shown to set fruit. 　　　Similar floral phenological and pollination ecological results were obtained for D. chinensis and D. trichophorum despite significant differences in floral architecture, as the former has six petals (typical of most other Annonaceae species), whilst the latter only has three. The results suggested that the substantial change in floral morphology in these two closely-related genera is probably non-adaptive as there is no change in pollination system. It is hypothesised that the morphological change is likely due to the disruption of homeotic gene expression during floral organ development. 　　　Studies of floral phenology and pollination ecology of Uvaria cordata revealed that it has a 3-day flowering rhythm and is pollinated by small beetles. The pollination ecology is unexpectedly similar to other species with typical beetle-pollination syndromes, although it lacks a pollination chamber and has pale-colored petals. It is suggested that species that lack a pollination chamber are more likely to be pollinated by guilds other than beetles or thrips as a floral chamber increases pollinator specificity. Several morphological and phenological characters are also presumably correlated with the evolution of generalist pollination to increase the pollination efficiency and assure fruit production, including torus shape, petal orientation, stigma shape, petal color, carpel and/or ovule number and the overlap of pistillate and staminate phases. 　　　Pseuduvaria is unusual in the Annonaceae as the majority of species possess unisexual flowers. Most species were previously interpreted as having staminate and structurally pistillate flowers, with infertile staminodes in the latter. The ‘pistillate’ flowers of P. mulgraveana are shown to produce viable pollen, however, contradicting this hypothesis. It is therefore recommended that floral unisexuality in the genus be reassessed by testing more species from different clades. Different strategies to promote xenogamy in the Annonaceae are reviewed, including protogyny, herkogamy, intra- and inter-individual phenological synchrony and dioecy. Three different mechanisms were recognized to achieve dioecy, including incomplete pollen development in hermaphroditic flowers, delayed anther dehiscence in hermaphroditic flowers and loss of androecium or gynoecium (with Pseuduvaria used as a paradigm). / 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

published_or_final_version / Ecology and Biodiversity / Doctoral / Doctor of Philosophy

published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy