Doctor of Philosophy (PhD)
The sedge family, Cyperaceae, is a large group with approximately 5,000 species distributed among ca. 100 genera. Sedges are economically and ethnobotanically important. They are conspicuous members of many floras around the world and provide vital food and cover for wildlife. The focus of this dissertation is on the genus Cyperus, which includes about 900 species. Due to its large size, advancements in knowledge of Cyperus are made in small “bites”. The molecular phylogenetics component of this research focused on New World Cyperus. Chapter 2 presents a phylogentic analysis employing sequences from the nuclear ITS region. Chapter 3 presents a more robust analysis using five genic loci, including sequences from nuclear ITS plus four plastid loci. This research was the first to estimate the phylogenetic position of the monotypic genus Karinia. Karina has been included in Cyperus in the past, and is here resolved as a member of the Ficinia clade which is consistently estimated as sister to the Cyperus clade in molecular studies. Karinia was embedded in a clade with Sciproides. Its morphology, including perennial habit, dense head-like inflorscences, and spirally-arranged floral scales, are consistent with that of Scirpoides. Another important result of this work is the resolution of the predominantly Central American Cyperus andinus and C. seslerioides as belonging to section Leucocephali. This study strongly supports section Leucocephali, whose members utilize C3 photosynthesis, as sister to C4 Cyperus. Members of section Leucocephali are adapted to open seasonally dry grasslands, which may be the ecological intermediary to the evolution of C4 photosynthesis. Sampling for molecular studies included in this research enabled assessment of two taxonomic sections: Luzuloidei and Diclidium. The New World section Luzuloidei, which is composed of C3 members, is strongly supported as monophyletic. A morphological synapomorphy in section Luzuloidei is the presence of two-keeled floral scales. Section Diclidium, which is diagnosed as having spikelets which break into one- to two-fruited segments upon maturity, is polyphyletic. Therefore, this unique mode of spikelet shattering arose independently at least twice. Results provided some insight into several taxonomic problems in the Umbellati group and in section Strigosi; however, a greater number of samples are needed to assess these problems. The suspected relationship of the North American prairie species Cyperus cephalanthus to the South American Cyperus rigens species group was confirmed by the molecular phylogenetic analyses, as was the monophyly of the C. rigens group. Cyperus cephalanthus strongly resembles the South American C. impolitus. It was hypothesized that these taxa were morpholically indistinguishable. Morphometric analysis showed that several characters are statistically different, includeing floral scale dimensions, achene width, and achene shape. However, results of Principal Components Analisis (PCA) suggest that Cyperus cephalanthus and C. impolitus are the same morphological species. Results of PCA of Cyperus rigens and several of its infraspecific taxa were inconclusive, highlighting the need for more work with this highly variable South American taxon. Coastal prairie is one of the most imperiled habitats in North America. It is in this habitat where Cyperus cephalanthus is found, with fewer than 20 known populations in North America (Louisiana and Texas). This research included a floristic survey of wet coastal prairie sites in southwestern Louisiana. This work was partly stimulated by the preference of Cyperus cephalanthus for this habitat, and further motivated by the discovery of several promising prairie remnants quadrupaling the aerial extent of known coastal prairie in Louisiana. The wet coastal prairie flora included 512 minimum-rank taxa, with 461 being native. A total of 255 were estimated to be ecological conservative and characteristic of coastal prairie, with the balance consisting of weedy elements taking advantage of disturbance and habitat alteration. The wet coastal prairie was rich in sedges, with 72 species among nine genera. Cyperus was the most species rich genus in the entire wet prairire flora with 20 species. Coefficients of conservatism (C-values) were assigned to each taxon in the wet prairie flora. These C-values will allow computation of various Floristic Quality Indices (FQI) for sites ranging from unplowed prairie remnants to de novo restorations.
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Reid, Christopher Simon, "Systematics of targeted flat sedges (Cyperus, Cyperaceae) of the Americas, including a floristic analysis of an imperiled sedge-rich prairie community" (2016). LSU Doctoral Dissertations. 4257.
Urbatsch, Lowell E.