Thesis (M. Sc.)--University of Canterbury, 2008. / Typescript (photocopy). Includes bibliographical references (leaves 105-112). Also available via the World Wide Web.

Several case studies at diffrent levels (population, regional, comparative etc.) were carried out to evaluate the importance of different sources of variation and to follow microevolutionary traits in Pilosella (Asteraceae). The gradient of different spatial levels and comparative studies of closely related taxa group (characterised by partly different type of ongoing microevolution - genus Picris) revealed some common processes while at the same time highlighted the uniqueness of genus Pilosella. Microevolutionary potential was studied at the population level using morphometric approach (hybridization tendencies of highly complex hybrid swarm in Prague - Praha Vysočany). Cytogeography of Pilosella officinarum was then investigated at the regional scale (Central Europe). Tetraploid cytotype was detected almost exclusively in Bohemia region and further to the west whereas pentaploid and hexaploid cytotypes prevailed in Moravia and Slovakia and further to south- east. Cytogeography was followed by morphometric evaluation of three most abundant ploidy levels (4x, 5x and 6x) of P. officinarum combined with the analyses of reproduction mode. Results confirmed the possibility to distinguish the particular cytotypes ...

Apomixis is an intriguing and agronomically valuable asexual reproductive pathway resulting in seeds that give rise to plants that are identical in genotype to the female parent. Apomixis is absent in agriculturally important seed crops and our work has focused on the analysis of apomixis in the daisy-like genus Hieracium which contains sexual and apomictic species. Prior studies have shown that apomixis in Hieracium is controlled by two dominant loci. The LOA controls the avoidance of meiosis during female gametophyte (embryo sac) formation and the LOP locus is required for fertilization independent embryo formation during seed initiation. The genes conferring apomixis are unknown. In this study we focused on the events of autonomous seed initiation. Cytological examination of apomictic mutants that have lost LOA or LOP and analysis of their progeny enabled us to characterize developmental aspects associated with the function of these loci. Upon removal of LOA meiosis occurs normally and LOP segregates with a 1:1 ratio in the progeny, characterizing maternal gametophytic control. We also show that autonomous embryo formation segregates with autonomous endosperm formation, suggesting that these two loci are closely linked. However, upon meiotic division, embryo lethal components arise and embryo development in apomeiosis mutants was generally defective and seed set was low. Similarly, upon removal of LOP, apomixis initiation occurs normally and unreduced embryo sacs can only form seeds if pollinated. Autonomous seed initiation is actively repressed in the sexual model plant Arabidopsis by the action of a chromatin remodelling complex encoded by the FERTILIZATION INDEPENDENT SEED (FIS)-class genes. These genes are homologues of the Drosophila PcG complex that also repress gene expression throughout Drosophila development. Mutations in the FIS-class genes lead to elements of apomixis, such as autonomous endosperm, and in one particular mutant, autonomous egg cell development. Given the similarity in apomictic and FISclass gene mutant phenotype we isolated three homologues from sexual and apomictic Hieracium plants: FERTILIZATION INDEPENDENT ENDOSPERM (FIE), MULTICOPY SUPPRESSOR OF IRA1 (MSI1) AND RETINOBLASTOMA (RBR). FIS-class genes from sexual and apomicit Hieracium and examined their expression, interaction and function during seed initiation. The isolated Hieracium FIS-class genes were highly conserved in sexual and apomictic plants in terms of gene sequence and temporal and spatial expression pattern. Analysis of protein interactions by yeast-two hybrid showed that the HFIE gene from sexual and apomictic plants does not interact with other complex members in the same manner found in Arabidopsis. Protein modelling uncovered structural differences between the Arabidopsis and Hieracium FIE proteins. RNAi- mediated down-regulation of HFIE in sexual Hieracium did not lead to autonomous seed initiation indicating HFIE was not part of a repressive complex. Down-regulation of HFIE in sexual and apomictic plants revealed the gene was essential for embryo growth and viability. Therefore, FIS-complex genes interact differently in Arabidopsis and Hieracium and have different developmental roles. In summary, the results presented here suggest that the FIS-genes are not mutated in apomictic Hieracium plants, but they interact differently relative to the Arabidopsis counterparts and play a fundamental role in embryogenesis. Thus, engineering autonomous seed into crops will not depend on mutating these genes but rather in uncovering the molecular signal that triggers apomictic development. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1337073 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2008

Hieracium pilosella is an invasive weed of New Zealand's short tussock grasslands. Since the 1960s, the abundance of H. pilosella has dramatically increased; it is now thought to occur in 6 million hectares of New Zealand (Espie, 2001), predominantly in grasslands. It is at least common in 42% of this area (Espie, 2001). Ecology is inherently spatial and as plants closely interact with their direct neighbours, the spatial arrangement of plants is vital to their functioning. A handful of recently published articles have implicated spatial structure of plant communities in theories of plant competition, resource use and the invasion of plant communities. The aims of this thesis were to: 1) determine if there are consistent spatial patterns in New Zealand's short tussock grasslands at relatively small scales (i.e. spatial relationships between individuals); 2) investigate how the invasion of H. pilosella may be altering these spatial patterns; and 3) establish if the spatial patterns of species, life-forms and root systems are being altered in different ways. Spatial patterns of both tussock and inter-tussock species, life-forms and root functional groups were evaluated at a range of short tussock grassland sites across a gradient of H. pilosella invasion levels in Canterbury, using both join-count statistics and Ripley's K-function. A classification system for the root functional groups of vascular species in these communities was developed and applied. It was found that species, life-forms and root functional groups in short tussock grasslands had generally consistent spatial patterns across sites both within and between species. These patterns were variable between significantly different levels of H. pilosella ground cover. The type of spatial pattern exhibited, and the way it was altered differed between species, life-form and root functional groups. For example, tussocks exhibited increased regularity up to scales of 160 cm and increasing aggregation at scales up to 500 cm, with increases in H. pilosella abundance. In contrast, both Agrostis capillaris and herbaceous chamaephytes had increased aggregation across scales up to 160 cm. These differences in spatial patterns along the gradient of invasion are a strong indication that H. pilosella is structurally fragmenting New Zealand's short tussock grasslands. This fragmentation is likely to have far reaching effects including the disturbance of invertebrate communities and the disruption of ecosystem services including pollination, vegetation regeneration, and nutrient cycling.

Hieracium pilosella is an invasive weed of New Zealand's short tussock grasslands. Since the 1960s, the abundance of H. pilosella has dramatically increased; it is now thought to occur in 6 million hectares of New Zealand (Espie, 2001), predominantly in grasslands. It is at least common in 42% of this area (Espie, 2001). Ecology is inherently spatial and as plants closely interact with their direct neighbours, the spatial arrangement of plants is vital to their functioning. A handful of recently published articles have implicated spatial structure of plant communities in theories of plant competition, resource use and the invasion of plant communities. The aims of this thesis were to: 1) determine if there are consistent spatial patterns in New Zealand's short tussock grasslands at relatively small scales (i.e. spatial relationships between individuals); 2) investigate how the invasion of H. pilosella may be altering these spatial patterns; and 3) establish if the spatial patterns of species, life-forms and root systems are being altered in different ways. Spatial patterns of both tussock and inter-tussock species, life-forms and root functional groups were evaluated at a range of short tussock grassland sites across a gradient of H. pilosella invasion levels in Canterbury, using both join-count statistics and Ripley's K-function. A classification system for the root functional groups of vascular species in these communities was developed and applied. It was found that species, life-forms and root functional groups in short tussock grasslands had generally consistent spatial patterns across sites both within and between species. These patterns were variable between significantly different levels of H. pilosella ground cover. The type of spatial pattern exhibited, and the way it was altered differed between species, life-form and root functional groups. For example, tussocks exhibited increased regularity up to scales of 160 cm and increasing aggregation at scales up to 500 cm, with increases in H. pilosella abundance. In contrast, both Agrostis capillaris and herbaceous chamaephytes had increased aggregation across scales up to 160 cm. These differences in spatial patterns along the gradient of invasion are a strong indication that H. pilosella is structurally fragmenting New Zealand's short tussock grasslands. This fragmentation is likely to have far reaching effects including the disturbance of invertebrate communities and the disruption of ecosystem services including pollination, vegetation regeneration, and nutrient cycling.

The hawkweed subgenus Hieracium s. str. is notoriously known for its extreme morphological variability and variation in ploidy levels that is associated with differences in modes of reproduction. Extensive past hybridization is supposed for the subgenus, but recent hybridization was evidenced only in few cases. The subgenus attracts the attention of botanists already for more than a century. Therefore the species diversity is largely examined and the taxonomy of the subgenus is well elaborated, although several contradictory taxonomic concepts exist. However the relationships among the species are unknown and haven't been studied yet. The investigation of these relationships from a phylogenetic perspective using molecular approaches was the main aim of the presented thesis. Basic species (both diploid and polyploid), representing morphologically unique taxa, that are supposed to be the basic evolutionary units of the subgenus were studied. The sequences of two intergenic spacers of the cpDNA (trnT-trnL and trnV-ndhC) and the external transcribed spacer of the nuclear ribosomal DNA (nrDNA ETS) were analyzed. Moreover, three new low-copy nuclear markers with higher variability than nrDNA and cpDNA markers were developed and their suitability for phylogenetic studies in Hieracium s. str. was...

Apomixis, or asexual seed development, if introduced into crop species, has the potential to greatly improve global food production. Towards this goal, this study focused on uncovering the genetic mechanisms that control the parthenogenesis step within apomixis whereby fertilisation is avoided. In the model apomict, Hieracium praealtum (Asteraceae), parthenogenesis is controlled by the LOSS OF PARTHENOGENESIS (LOP) locus. Previous research showed that in addition to genomic copies of candidate genes at LOP, the genome has at least three other copies referred to as alternative alleles. The main goal of this study was to investigate four candidate genes, Genes B, X, H and Y, at LOP by generating segregation data of the alternative alleles. BAC clones containing alternative allele sequences were identified and Roche 454 pyrosequenced. These sequences were used to design alternative allele specific primers for genotyping two Hieracium praealtum polyhaploid populations (~ 300 plants). Four major conclusions were drawn from this study. First, the alternative alleles were in fact acting like alleles to the LOP alleles of Genes B, X and Y. Second, allelic sequence divergence (ASD) of the LOP alleles of Genes B and X relative to the alternative alleles, indicated a recent and separate evolutionary history. Third and, unexpectedly, recombination was detected at the LOP locus, in contrast to other apomixis loci reported in the literature. Furthermore, Gene B was found to be very closely associated with parthenogenesis in the polyhaploid population indicating that it may be essential to parthenogenesis and therefore requires further investigation. On the other hand, the absence of Genes X, Y and H, due to recombination, had no impact upon parthenogenesis. Fourth, the sequence data suggested that the LOP and alternative alleles originated from a shared common allele ancestor. It is hoped that these findings have made a significant contribution towards the future goal of introducing apomixis into crop species.

Hieracium lepidulum is an invasive weed in New Zealand. It colonises a wide range of habitats including pine plantations, scrubland, native Nothofagus forest, and mid-altitude to alpine tussock grassland, where it is competing with indigenous species. Understanding the breeding systems and population genetic structure of H. lepidulum is important for biocontrol, and aids in the understanding of evolutionary colonisation processes. H. lepidulum is a triploid, diplosporous, obligate apomict. This type of reproduction through clonal seed does not involve meiosis or fertilisation, and theoretically populations should contain very low levels of genetic variation, the only source being somatic mutation. Common garden experiments and microsatellite markers were used to determine the population genetic structure of H. lepidulum populations in the Craigieburn Range, Canterbury. Both experiments revealed that populations, sampled from three replicate altitudes within three geographically-separated locations, contained no genetic variation; individuals all possessed the same microsatellite genotype. These results strongly suggest that the Craigieburn Range H. lepidulum individuals reproduce solely by apomixis and populations belong to the same clonal lineage. Populations were also examined for their response to two abiotic environmental ‘stresses’, drought and shade. H. lepidulum populations’ exhibited high drought tolerance, yet appeared to be shade-intolerant. Low levels of reproduction in light-limiting habitats will prevent the invasion of H. lepidulum into closed-canopy forest habitats. H. lepidulum appears to have overcome the reduction in fitness associated with apomictic reproduction by phenotypic plasticity, fixed heterozygosity and polyploidy – all associated with increased vigour, fitness, and the ability to occupy broader ecological niches. This study’s results are hopeful for the development of biocontrol programs involving genotype-specific pathogens but suggest that grazing management may not succeed. The data will be useful for future comparisons of genetic structure during the course of H. lepidulum invasions and will contribute to the management of this invasive weed.

Hieracium lepidulum is an invasive weed in New Zealand. It colonises a wide range of habitats including pine plantations, scrubland, native Nothofagus forest, and mid-altitude to alpine tussock grassland, where it is competing with indigenous species. Understanding the breeding systems and population genetic structure of H. lepidulum is important for biocontrol, and aids in the understanding of evolutionary colonisation processes. H. lepidulum is a triploid, diplosporous, obligate apomict. This type of reproduction through clonal seed does not involve meiosis or fertilisation, and theoretically populations should contain very low levels of genetic variation, the only source being somatic mutation. Common garden experiments and microsatellite markers were used to determine the population genetic structure of H. lepidulum populations in the Craigieburn Range, Canterbury. Both experiments revealed that populations, sampled from three replicate altitudes within three geographically-separated locations, contained no genetic variation; individuals all possessed the same microsatellite genotype. These results strongly suggest that the Craigieburn Range H. lepidulum individuals reproduce solely by apomixis and populations belong to the same clonal lineage. Populations were also examined for their response to two abiotic environmental ‘stresses’, drought and shade. H. lepidulum populations’ exhibited high drought tolerance, yet appeared to be shade-intolerant. Low levels of reproduction in light-limiting habitats will prevent the invasion of H. lepidulum into closed-canopy forest habitats. H. lepidulum appears to have overcome the reduction in fitness associated with apomictic reproduction by phenotypic plasticity, fixed heterozygosity and polyploidy – all associated with increased vigour, fitness, and the ability to occupy broader ecological niches. This study’s results are hopeful for the development of biocontrol programs involving genotype-specific pathogens but suggest that grazing management may not succeed. The data will be useful for future comparisons of genetic structure during the course of H. lepidulum invasions and will contribute to the management of this invasive weed.

New Zealand's South Island tussock grasslands have been highly modified by human activities, including burning, grazing and introductions of exotic plants for pastoralism. Studies suggest that tussock grasslands are degraded, in that native species have declined, and exotic species have increased in both diversity and abundance. These trends are primarily thought to be related to the impacts of grazing and subsequent grazing removal. Few studies have assessed long-term changes that have occurred in tussock grasslands, and those that have are generally limited to one particular location. This thesis aimed to investigate temporal changes in community structure in tussock grasslands, and relate these changes to environmental variables and land tenure. Data were used from 90 permanently-marked vegetation transects, which were set up on 19 geographically widespread properties in areas of tussock grassland across Canterbury and Otago in the South Island of New Zealand. The transects were on land in both conservation and pastoral tenure. Each transect was 100 m, and consisted of 50 0.25 m² quadrats. The transects were measured between 1982 and 1986 (first measurement), were re-measured between 1993 and 1999 (second measurement) and again between 2005 and 2006 (third measurement). A total of 347 vascular species were observed over the 90 transects and three measurement times. Species richness declined between the first and second measurements (first time interval), and increased between the second and third measurements (second time interval), at both the small (quadrat) and large (transect) scales. Both native and exotic species declined in mean quadrat species richness during the first time interval, and then increased during the second time interval. Changes in mean quadrat species richness were similar on transects in both conservation and pastoral tenure. Multivariate analysis of species' occurrences in quadrats identified a long gradient in species composition for these 90 transects. Four key plant communities were identifed along this gradient and differed in their mean elevation: (1) Highly-modified pastoral community, (2) Short-tussock grassland community, (3) Tall-tussock grassland community, (4) Alpine mat-forming species community. A detailed investigation into temporal changes that occurred on 53 transects that occurred in short- and tall-tussock grassland communities showed that changes in species composition were not consistent over time. Transects on different properties changed in species composition by different amounts. Specifically, in ordination space, transects on two properties changed in composition significantly more than transects on one other property. The property that a transect was on also affected the way that it changed in composition, i.e. native species were more likely to have increased on transects on some properties. Transects in conservation tenure did not change in species richness or composition differently from those in pastoral tenure. Considering that many native plants in tussock grasslands are relatively slow-growing, and that these areas have been grazed and burned for more than a century, we may expect it to be some time before we can detect differences in vegetation dynamics on conservation land from that on pastoral land. The changes in the community structure of these tussock grasslands were related to a combination of environmental factors, such as soil chemistry, climate, and management factors. This study has allowed greater understanding of vegetation change in tussock grasslands, and demonstrates the importance of long-term ecological monitoring in making reliable and accurate predictions about landscape-scale changes in tussock grassland community structure.