Xyris tennesseensis: status survey, habitat restoration/management concerns, and relation to a new xyrid, Xyris spathifolia
Type of DegreeDissertation
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Xyris tennesseensis is a federally endangered, obligate wetland, perennial herb. It inhabits calcareous seeps, fens, and spring runs with a distribution restricted to the Interior Plateau and Ridge and Valley ecoregions in Alabama, Georgia, and Tennessee. The NatureServe network ranks this species as critically imperiled in each of the states in which it occurs, and imperiled overall. Given its specificity of habitat, limited distribution, and rarity/threat of extinction, Xyris tennesseensis is of considerable interest to the conservation community and to those entities charged with managing its populations. Results of a two-year U.S. Fish & Wildlife Service sponsored status survey of X. tennesseensis populations are reported here, as are the results from a three-year Georgia Department of Transportation supported habitat restoration study of X. tennesseensis habitat. Serendipitously, during the USFWS status survey, a new species of Xyris, rarer still than X. tennesseensis, was discovered in the Ketona Glades of Bibb Co., AL, and is described and figured herein. A status survey of 19 X. tennessensis populations confirmed this species’ habitat specificity and tenuousness existence. Xyris tennesseensis sites were typically quite small with a mean area of ca. 500 m2. Average population size was ca. 3,500 ramets (individual plants), although over 50% of the populations contained fewer than 1,000 ramets. Numbers of flowering spikes and seedlings were highly variable among sites, ranging from ca. 30 to 20,900, and from 0 to 7,900, respectively. A three-year habitat restoration/management study was conducted to determine effects of the cutting of shrubs that were shading a population of X. tennesseensis on public land. Shrub cutting significantly increased flowering of Xyris on the site, although this effect was short-lived (only 2 years). There was also a significant increase in seedling production, but not total numbers of ramets. Floral visits were significantly more frequent to Xyris flowers located on cut plots. There was no Xyris seed bank found. While cutting shrubs can stimulate Xyris reproduction, it must be applied frequently in order to address woody regrowth and rapid development of herbaceous/graminoid competition. A distinctive new xyrid from one of the Ketona Glades was found growing intermixed with X. tennesseensis, but is distinct from it. I distinguish this new taxon, Xyris spathifolia Kral & Moffett, from the latter, giving it species rank based upon observations of field-collected material, common garden trials, and herbarium surveys.