School of Botany - Theses
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ItemMolecular systematics, biogeography, and taxonomy of the fern family Aspleniaceae in Australasia and the south-west Pacific( 2014)Aspleniaceae is one of the largest fern families with around 700 species distributed on all continents except Antarctica. Three genera, Asplenium L., Pleurosorus Fee and Hymenasplenium Hayata, and around 115 species occur in the Australasian and south-west Pacific region from New Guinea south to Australia and New Zealand and east to Fiji. Amongst the Aspleniaceae of this region are various species of interest to molecular study including several species of uncertain taxonomic status, several species complexes and contrasting widespread and localised species distributions. However, molecular systematic studies of Aspleniaceae from much of this region has been lacking when compared with some other parts of the world. This study presents the first thorough molecular systematic investigation of the Aspleniaceae throughout Australasia and the south-west Pacific, incorporating 70 Aspleniaceae species and 325 collections from this region. The chloroplast regions rbcL, trnL-F, rps4 and rps4-trnS were sequenced for representative populations of all species sampled. These sequences were used to construct phylogenies in order to gain a thorough understanding of the relationships between the Aspleniaceae of Australasia and the south-west Pacific and how they are related to Aspleniaceae elsewhere. Chloroplast haplotype networks were also constructed to study the relationships among populations of closely related or genetically variable species and to infer the phylogeography of A. flabellifolium Cav. Amplified Fragment Length Polymorphisms (AFLPs) and nuclear pgiC and gapCp sequences were obtained in addition to chloroplast sequences for the Australian A. paleaceum R.Br. complex. Phylogenetic analyses of chloroplast and nuclear sequences and phenetic analyses of AFLP data were used to resolve lineages present within the A. paleaceum complex and determine the relationships between these lineages. Molecular findings in conjunction with morphological examination were used as a basis for taxonomic revision of the Aspleniaceae of Australia. Chloroplast phylogenies demonstrated that the Australasian and south-west Pacific Aspleniaceae belong to six major clades that are widespread outside of this region and that locally endemic species were generally most closely related to widespread species or species endemic to elsewhere. The vast majority of species were placed in two of the six major clades, with the remaining clades each containing four or less species. One of the two larger clades was largely composed of a predominately temperate ‘Austral’ group, which also contained some tropical south-west Pacific species, and a mostly tropical, but non-monophyletic section Thamnopteris. The other well-represented clade was mostly composed of tropical species. Amongst the minor clades were a Hymenasplenium clade, sister to the remaining Aspleniaceae, and a clade nested within Asplenium, which contained Pleurosorus. The position of these genera in the phylogenies supports recognition of the genus Hymenasplenium and the inclusion of Pleurosorus in Asplenium. A new combination Hymenasplenium wildii (F.M.Bailey) D.Ohlsen, Brownsey & Perrie is proposed for A. wildii F.M.Bailey to account for the placement of this Australian endemic species within Hymenasplenium. Several species were shown in chloroplast phylogenies to be non-monophyletic, including several inter-continental species, and consequently need taxonomic revision. Such taxonomic revisions require further investigation involving widespread sampling and thorough morphological and molecular study. Several taxa that are not easily assigned to the current Australian species also required taxonomic study. A new species, A. windsorense D.Ohlsen & Brownsey, is here described to account for one of these taxa. This species shares the greatest morphological similarity to A. athertonense S.B.Andrews, but its inclusion within that species would have rendered it non-monophyletic. In addition, two new Asplenium species records, A. caudatum G.Forst. s.l. and A. longissimum Blume, were formally added to the Asplenium flora of Australia. However, one putative new Australian Asplenium species was shown to be misplaced in Aspleniaceae. In chloroplast phylogenies this species was nested within the genus Diplazium Sw., sister to a species that has been placed in a separate genus, Callipteris Bory. Comparison with type material determined that this taxon is a new Australian record of the previously described Papua New Guinean Diplazium squamuligerum (Rosenst.) Parris. The phylogenetic position of this species was confirmed by scale features. The greatest intraspecific genetic variation was detected in A. flabellifolium Cav. High haplotype diversity in south-east Australia suggests that this species has had a long-term presence throughout this part of its distribution. The distribution of haplotypes and their position in the networks suggest that A. flabellifolium has been involved in frequent long-distance dispersal across its distribution, with at least five long-distance dispersals inferred to account for its trans-Tasman distribution. Surveys of genetic variation among the Australian Aspleniaceae also support recognition of all Australian species of section Thamnopteris. Conversely, a lack of concordance between morphology and genetic variation reject recognition of P. subglandulosus (Hook. & Grev.) Tindale and consequently all Australasian Pleurosorus are included in a single species, A. subglandulosum (Hook. & Grev.) Salva, Prada & T.E.Diaz. Chloroplast variation was low between sampled accessions of the A. paleaceum complex and of limited utility in defining lineages amongst this complex. However, more variable AFLPs revealed the presence of five groups. These groups were considered to represent separate species, but included some hybrids. Morphological features characteristic of each AFLP group are used to redefine species boundaries in the complex. However, morphological characters that will diagnose one of the groups, the A. attenuatum var. indivisum group, need to be established with further sampling and investigation. Chloroplast regions, nuclear pgiC, and morphology show that a population of uncertain taxonomic status from Kroombit Tops National Park are fertile hybrids between A. polyodon G. Forst. and most likely A. paleaceum of the A. paleaceum complex. However, relationships between other taxa involved in the A. paleaceum complex need to be confirmed with further study of more collections using additional molecular markers and chromosome counts. In summary, six additional species, including Diplazium squamuligerum, and one new genus Hymenasplenium are recognised in Australia. Two of these species reside among Australian representatives of the A. polyodon complex and their taxonomic treatment is postponed until a thorough investigation of the complex across its entire distribution is undertaken. One species, Pleurosorus subglandulosus and one genus Pleurosorus are also no longer recognised. This gives a net increase of four Aspleniaceae species for Australia to bring the number of Apleniaceae species here recognised in Australia to 42 in two genera.
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ItemThe regulation of SnRK1 from Arabidopsis thaliana( 2013)An intrinsic characteristic of all life is the ability to regulate the organism’s internal energy status despite sometimes wildly fluctuating conditions in the external environment. SnRK1 (SNF1-related kinase 1) is the plant orthologue of an evolutionarily conserved, energy-sensing, eukaryotic protein kinase family, including SNF1 from yeast and AMPK from mammals, that plays a major role in the regulation of both cellular and systemic energy homeostasis. The family is functional as heterotrimeric holoenzymes comprising catalytic α¬ and regulatory β and γ subunits, each consisting of several functional domains and each of which may exist in multiple isoforms giving rise to various isoenzymes. Plants contain genes encoding isoforms for each of these subunit types, some of which display unique domain architecture not found outside the plant kingdom. Whilst SNF1 and AMPK have been extensively studied, relatively little is known of how the SnRK1 holoenzyme from plants is regulated and how the various subunit isoforms and their respective functional domains contribute to this regulation. This thesis addresses several aspects of SnRK1 regulation by using biochemical, molecular, and genetic techniques. The present work has described SnRK1 from the model plant Arabidopsis thaliana as a heterotrimeric complex in vitro, existing in six isoenzyme combinations, comprising both classical-type SNF1/AMPK subunits and non-typical plant isoforms, these subunit interactions being confirmed in vivo, with the plant-specific βγ determined to be the sole γ-type subunit. SnRK1, like SNF1 and AMPK, is only minimally active as individual catalytic subunits indicating that SnRK1 is functional as a heterotrimer. Whilst phosphorylation of the α-subunit T-loop threonine is critical for activity this residue is resistant to dephosphorylation by phosphoprotein phosphatases signifying a major divergence in mode of regulation in comparison to SNF1 and AMPK. In addition, whilst the β-subunit carbohydrate-binding modules of AMPK bind glycogen, those of SnRK1 unexpectedly do not associate with glycogen, starch, or a vast array of oligosaccharides and plant-derived polysaccharides. Genetic and molecular studies focused on the β2 subunit. Analysis of T-DNA insertion mutations in this gene suggest that β2, whilst not drastically impacting plant phenotype under normal growth condition, does reduce the plant’s extent of growth. When the dark period was extended, however, the β2 mutants appeared to suffer from a starch rationing phenotype, not being able to conserve transient leaf starch as in wild-type plants. Using the GUS reporter system, β2 gene expression was observed strongly in vascular tissue, some floral tissue, and the floral organ abscission zone. Finally, in accordance with SnRK1’s role as a central integrator of metabolism, the β2 protein was observed to be localised mainly to the cytoplasm and nucleus by way of fusion to the yellow fluorescent protein. This thesis has contributed to the growing body of knowledge regarding SnRK1 with several of the findings prompting modification to assumptions regarding the regulation of the enzyme. These findings indicate that the central metabolic regulator, whilst conserving many features, is regulated in a considerably different manner to that of its yeast and mammalian orthologues, likely reflecting the unique metabolism of the plant life-style.
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ItemThe natural vegetation pattern of the Mornington Peninsula, with particular reference to the genus Eucalyptus( 1972)The natural vegetation pattern of the Mornington Peninsula, Victoria, has been studied and presented in map form on the basis of: Environmental factors associated with eucalypt distribution and habit are discussed. Vegetation formations are described and evidence presented of dependence on changing equilibria of environmental factors particularly pedological factors. Data obtained from transects across salt marshes are discussed. This indicates the inadequacy of presently available information regarding the delicately balanced environment of this formation. Difficulties in determination and delineation of plant associations are discussed. Because of species gradations it was not possible to satisfactorily separate all associations by subjective determinations alone. Abrupt discontinuity in one or more environmental factors makes it possible to subjectively determine five plant associations. A further twenty associations were determined by computer analysis of qualitative floristic lists. Delineation and problems of field recognition of these twenty statistical associations is discussed with reference to the work of Braun-Blanquet and of Poore. A preliminary attempt is made to correlate environmental factors with distribution of Eucalyptus spp., of vegetation formations, and of plant associations. Appendices include descriptions of soil types in the region; historical evidence which relates to past condition and management of the vegetation; and field data.