Apomixis is an evolutionarily important phenomenon across plant lineages. The interaction of apomixis with hybridization and polyploidy can lead to complex patterns of reticulation, complicating efforts to reconstruct evolutionary history in groups where apomixis is common. Ferns, in particular, are rich in apomictic species, notably in centers of species diversity like East Asia. Eastern North America too is home to a number of apomictic species. We investigated the East Asian ferns in Polystichum sections Xiphopolystichum and Duropolystichum (Dryopteridaceae) in order to elucidate the evolutionary and biogeraphic history of seven apomictic species in the group: Polystichum tsus-simense, P. xiphophyllum, P. sinotsus-simense, P. pseudoxiphophyllum, P. mayebarae. P. rigens, and P. neolobatum. In addition, we examined the evolutionary origin of an undescribed apomictic cytotype of North American genus Phegopteris (Thelypteridaceae). The datasets comprised phylogenetic inference based on three nuclear and three plastid markers, analysis of mixed nucleotide signals from chromatograms generated from Sanger sequencing of nuclear markers, ploidy estimates based on flow cytometry data and spore length measurements, morphometric analysis of representative specimens collected in southwest China and nearby regions, and climatic niche models. By interpreting these multiple lines of evidence synthetically, we have discerned multiple highly reticulate complexes of polyploid lineages derived largely from diploid sexual progenitors. Our findings highlight the importance of understanding the role of apomictic reproduction in the context of species diversity, an understanding central to similar future inquiry into the diversity of East Asian and North American ferns.

Thesis (M.S.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains ix, 124 p. : ill. Vita. Includes abstract. Includes bibliographical references.

Diss. (sammanfattning) Stockholm : Univ., 2007. / Härtill 4 uppsatser.

Thesis (Ph. D.)--University of Oregon, 2007. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 201-241). Also available for download via the World Wide Web; free to University of Oregon users.

Thesis (Ph. D.)--University of Washington, 1990. / Vita. Includes bibliographical references (leaves [109]-120).

Thesis (M.A.)--York University, 2007. Graduate Programme in Biology. / Typescript. Includes bibliographical references (leaves 53-63). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR31999

The genus Sorbus is an example of a taxonomically complex group (TCG) with diversity derived from hybridisation, polyploidy and apomixis. The focus of this study was to elucidate the evolutionary relationships among nine Sorbus species including endemics of the Devon and north Somerset region of the south west UK, determine main routes of polyploid formation and investigate reproductive sustainability in order to make recommendations for Sorbus conservation. Molecular analysis showed that genetic structure patterns and genotypic diversity support the hypothesis that the study polyploids are a product of rare interspecific hybridisation, of single origins and are maintained through apomictic reproduction. PCoA, Neighbour Joining analysis and parental simulations reveal a reticulated relationship, with diversification the result of hybridisations between sexual diploid Sorbus torminalis and both tetraploid and triploid species. Hybridisation between S. torminalis and tetraploid Sorbus margaretae (subgenus Aria) have likely given rise to the study members of subgenus Tormaria through production of a triploid which has subsequently backcrossed to Sorbus torminalis to form further tetraploids. The discovery of a cryptic hybrid in subgenus Aria also suggests occasional hybridisation events among tetraploids are a possible route for further tetraploid formation These events illustrate key routes of polyploid formation, both illustrating the role of triploids in tetraploid formation via the triploid bridge and the key role in sexual diploids in diversification in Sorbus. Hand pollination experiments showed that self-incompatibility in the triploid species (Sorbus subcuneata) means reliance on congeneric pollen from sympatric tetraploid species for seed production. Reproductive sustainability in this species is severely compromised through spatial isolation from compatible congeners. Our findings are strong support for the development of conservation strategies that aim to safeguard current diversity through actions that increase reproductive sustainability and recruitment opportunities, and promote opportunities for on-going hybridisation for future diversification of Sorbus in this region.

Doctor of Philosophy / Department of Plant Pathology / Bikram S. Gill / Wheat is the most widely grown and consumed grain crop in the world. In order to meet future agricultural production requirements of a growing population, it is essential that we achieve an increased understanding of the basic components and mechanisms shaping growth and productivity of the polyploid wheat plant. Fusarium head blight (FHB) (syn. "scab") poses a serious threat to the quantity and safety of the world's food supply. The resistance locus Fhb1 has provided partial resistance to FHB of wheat for nearly four decades. Map-based cloning of Fhb1 is justified by its significant and consistent effects on reducing disease levels, the importance of FHB in global wheat production and food safety, and because this gene confers partial resistance to this disease and does not appear to behave in a gene-for-gene manner. A bacterial artificial chromosome (BAC) contig spanning the Fhb1 region was developed from the cultivar 'Chinese Spring', sequenced and seven candidate genes were identified in an ~250 kb region. Cosmid clones for each of the seven candidate genes were isolated from a line containing Fhb1 and used for genetic transformation by biolistic bombardment. Transgenic lines were recovered for five candidate genes and evaluated for FHB resistance. All failed to complement the Fhb1 phenotype. Fhb1 is possibly one of the two remaining candidate genes, an unknown regulatory element in this region, or is not present in Chinese Spring. Traditional views on the effects of polyploidy in allohexaploid wheat have primarily emphasized aspects of coding sequence variation and the enhanced potential to acquire new gene functions through mutation of redundant loci. At the same time, the extent and significance of regulatory variation has been relatively unexplored. Recent investigations have suggested that differential expression of homoeologous transcripts, or subfunctionalization, is common in natural bread wheat. In order to establish a timeline for such regulatory changes and estimate the frequency of non-additive expression of homoeologous transcripts in newly formed T. aestivum, gene expression was characterized in a synthetic T. aestivum line and its T. turgidum and Aegilops tauschii parents by cDNA-SSCP and microarray expression experiments. The cDNA-SSCP analysis of 30 arbitrarily selected homoeologous transcripts revealed that four (~13%) showed differential expression of homoeoalleles in seedling leaf tissue of synthetic T. aestivum. In microarray expression experiments, synthetic T. aestivum gene expression was compared to mid-parent expression level estimates calculated from parental expression levels. Approximately 16% of genes were inferred to display non-additive expression in synthetic T. aestivum. Six homoeologous transcripts classified as non-additively expressed in microarray experiments were characterized by cDNA-SSCP. Expression patterns of these six transcripts suggest that cis-acting regulatory variation is often responsible for non-additive gene expression levels. These results demonstrate that allopolyploidization, per se, results in rapid initiation of differential expression of homoeologous loci and non-additive gene expression in synthetic T. aestivum.

Somatic tissues in mature copepods are determinate in growth, not undergoing mitosis; cell number remains constant throughout adult life. Here we report evidence of polyploidization for eight species of cyclopoid copepods. Using static Feulgen-DNA cytophotometry, we measured individual somatic nuclei in populations of Eucyclops ensifer from Brazil and of Eucyclops agilis from Ohio, U.S.A. Small but potentiality significant percentages of the adult somatic cells in these species, as well as in Bryocyclops caroli, Halicyclops tagea, Macrocyclops albidus, Mesocyclops edax, Mesocyclops thermocyclopoides, and Thermocyclops decipiens, contained at least twice (4C) the amount of DNA found in their diploid (2C) cells. These species have 2C DNA values that are representative of the range of genome sizes in cyclopoid copepods which, as a group, have much smaller genomes than calanoid copepods. Polyploidy may be a previously unrecognized mechanism whereby copepods alter the DNA content or nucleotype during specific stages in development. DNA reduplication preceding a cycle of endomitosis may result in a doubling of the functional genome, thus providing additional template for mRNA transcription related to specific functions.

Order Acipenseriformes (sturgeons and paddlefishes) is an ancient lineage of bony fishes (> 200 million years old) with most extant species at conservation risk. The pallid sturgeon, Scaphirhynchus albus, is a federally endangered species native to the Mississippi and Missouri River basins. Hybridization with sympatric shovelnose sturgeon, S. platorynchus, is one of several threats to pallid sturgeon. Current molecular markers cannot reliably distinguish among pure species and multigenerational backcrosses. This information is critical for implementation of management strategies to increase populations through natural reproduction and artificial propagation. Genotypes from a large panel of unlinked single-nucleotide polymorphisms (SNPs) may provide greater resolution of the two species; however, paralogous sequence variants (PSVs) within individuals resulting from an ancient whole genome duplication event confound SNP development. The aim of this dissertation was to produce unlinked disomic SNPs that would increases resolution between pallid sturgeon and shovelnose sturgeon. This was achieved by producing haploid gynogens, which contain only DNA from the maternal parent, and then producing a reference from these haploid gynogens. Sequence assembly based on haploids informed the presence of multi-locus contigs. More than 11,000 disomic SNP markers were produced that differentiate between the two species by mapping 120 individuals of either species onto the haploid reference. A linkage map, based on three haploid families, was able to resolve some paralogs and can be used to inform which discriminatory SNP markers are linked. Future research should convert the disomic markers derived in this study to an applied form, such as that achieved by genotyping-by-thousands.