Systematics of targeted flat sedges (Cyperus, Cyperaceae) of the Americas, including a floristic analysis of an imperiled sedge-rich prairie community

Abstract

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