Prevalence of sexual and asexual reproduction by plants influences genetic and spatial structure of populations. We investigated reproduction in five populations of Dirca palustris that span its distribution from Florida to North Dakota, and identified the contributions of sexual and asexual reproduction to the clustering of individuals that is characteristic of the species. In each population, maximum density of plants was documented by assessing the 10 clusters that appeared most dense. We surveyed these clusters for evidence of recent recruitment, sowed locally collected fruits to estimate potential for germination, and estimated prevalence of clones by using ISSR genetic markers. Maximum density of plants varied markedly among populations, and denser clusters showed evidence of greater recruitment over several years. Germination of seeds one year after fruits were sown varied from 7 to 56% among populations. Genetic analysis, and our observation of cotelydonary scars on young plants, indicate restricted seed dispersal rather than clonal reproduction explains the occurrence of D. palustris in clumps. Plant density and recruitment were greatest in North Dakota, which raises questions about what governs the distribution of D. palustris at this northern and western limit of the species. The population in Florida, where the species is listed as endangered at its southern limit, had the least germination, the greatest extent of granivory, and relatively poor evidence for recent recruitment. D. palustris is rare in the southern portion of its range, and our data demonstrate the population in Florida should be prioritized by conservationists and monitored for recruitment.

Native old-field pineland with hardwood undergrowth was replaced 42 years later by alien hardwood forest dominated by invasive species at Goodwood forest in Tallahassee, Florida. Cinnamomum camphora dominated the overstory and Ardisia crenata the undergrowth. Succession theory would have anticipated development to native southern mixed hardwood forest or a subset called magnolia-beech forest. The initial native old-field forest community, prior to alien colonization, was characterized mostly by Pinus taeda, Quercus nigra, Liquidambar styraciflua and other lowland trees that were not likely to persist indefinitely on uplands. These trees colonized abandoned fields on account of a dearth of seed sources for oak-hickory forest trees which occupied these well drained uplands in the 18th century. Oak-hickory forest had been removed in the 19th century to allow the cultivation of cotton, and there was no evidence that it would recover at Goodwood forest.

Study of the pollination biology of endangered species can provide useful information for natural resource managers. We studied the floral biology of Xyris tennesseensis, a federally endangered species, at a site (Willett Springs) in north central Alabama. We described floral behavior and flowering phenology, supplemented pollen onto stigmas from self and outcross sources to determine its effect on seed production and germination ability, documented the floral visitor fauna, and collected data on behavior, abundance and pollen loads of floral visitor species during two years (1998–99). Flowering of the population lasted from July to September each year, but individual flowers completed blooming in about a 3-hr period beginning in late morning. On average, a single flower was visited by three insects for a total of five floral visits during its brief period of anthesis. Floral visitation was greatest when flowers first opened and declined steeply by the time flowers began to close. Halictid bees were the most abundant floral visitors, along with four species of pollen-consuming syrphid flies. Based upon quantity of pollen carried, location on the body, and visitation frequency, we concluded that the halictid bee Lasioglossum zephyrum was the single most important pollinator species on the study site. However, the pollen supplementation study showed that flowers produce seeds without visitation by insects, likely by self-pollination. We concluded that, unlike some endangered plant species, insect pollination is not required for seed production by X. tennesseensis.

Dalea species are legumes that often are included in seed mixtures used for prairie restorations. Three Dalea species (D. foliosa, D. candida, and D. purpurea) exhibit two different types of seeds: plump (well-rounded larger) and dented (wrinkled smaller) seeds. Differences in germination and viability of these two types of seeds have not been reported. Our objectives were to compare seed mass, germination and viability between these types of seeds for three Illinois Dalea species. Fruits were collected for D. foliosa from 1998–2001 (Will County) and for D. candida and D. purpurea from 2001–2003 (Kankakee, Tazewell and Will Counties). For each species, seed mass, germination and viability were determined per seed type (plump or dented). Seed mass was significantly higher for plump than dented seeds for all three species. For D. foliosa and D. candida, germination of dented seed exceeded that of plump seed in some years. For D. purpurea, germination was significantly greater for plump seeds in both years. For ungerminated seeds of D. foliosa, only the plump seeds were viable, whereas for D. candida and D. purpurea, both seed types were viable. A comparison of seed germination among all three species when collected in the same county and year showed lower germination for D. foliosa than for D. candida and D. purpurea. In summary, seed types play a significant role in germination of these three species, and D. foliosa has lower germination than D. candida or D. purpurea.

Didiplis diandra is a small shoreline aquatic plant scattered throughout eastern North America. In the Atlantic coast states from Virginia to Georgia it has been confused with other species that grow in similar habitats. Leaves of D. diandra are heterophyllous, submersed leaves average 15.4 mm long while emersed leaves average 6.3 mm long. A taxonomic key is presented to aid in identification of small shallow water and shoreline aquatic plants including members of the genera Callitriche, Crassula, Elatine and Ludwigia.

Assessments of stream biology are prerequisites to developing watershed management plans to improve ecological integrity. We sampled six streams in the Red River Watershed of North-Central Tennessee to evaluate the effects of non-point source pollution on diatom assemblages, primary production, and potential for excessive algal growth. We used diatom indices to assess the structure of diatom assemblages, changes of oxygen concentrations to evaluate primary production, and growth dynamics of the green alga Selenastrum capricornutum to evaluate the potential for excessive algal growth. The three most abundant diatom taxa collected were Nitzschia linearis (16%), Navicula reichardtiana (15%), and Navicula tripunctata (7%). Habitat impairment in all six streams is indicated by: (1) high Siltation Index values for diatom assemblages which indicate loss of biotic integrity as a result of excessive sediments from erosion, (2) high rates of whole-stream oxygen metabolism characteristic of eutrophic conditions, (3) low ratios of whole-stream gross primary production to respiration distinctive of heterotroph-dominated habitats often associated with poor quality water, and (4) high carrying capacities for Selenastrum capricornutum indicative of nutrient enrichment. High values of the Trophic Diatom Index and low values of the Pollution Tolerance Index of diatom assemblages at five of the six stream sites signify impairment due to eutrophication. The results reveal the impacts of excessive sediments and nutrient enrichment on the structure of diatom assemblages, oxygen dynamics, and potential for excessive algal growth in streams of the Red River Watershed.

A survey of grasses from the Flat Rock Cedar Glades and Barrens State Natural Area in Murfreesboro, Tennessee was undertaken during the 2008 growing season with the goal of creating a comprehensive list of grass species living in a single glade environment. Twenty four different species were identified during the survey. All had been previously recorded in Tennessee but two had not been noted in cedar glades, Sprorobilus clandestinus and Elymus hystrix, and one, Dichanthelium scoparium, had not been demonstrated in Rutherford County. The survey also provides information on species distribution within the glade, amount of sunlight exposure, and flowering time within the growing season. The plastid matK and rbcL genes and the trnH-psbA intergenic spacer region were sequenced from the specimens and are cataloged in GenBank. Variance analysis of matK and rbcL loci was conducted with the sequences produced in this study as well as GenBank archived sequences from other grasses. Our data conservatively suggest that the Consortium for the Barcode of Life (CBOL) recommended loci, matK and rbcL, should enable Poaceae species identification with 95% accuracy.

A new species, Leitneria pilosa, and a new subspecies, L. pilosa subsp. ozarkana, are described based on leaf morphology, ISSR polymorphisms, ITS sequence character, and geographical isolation. Our infrageneric assessment of populations of Leitneria showed that L. pilosa, which occurs as western disjunct populations in Missouri, Arkansas, and Texas, has undergone species-level divergence from plants of Leitneria floridana indigenous to Florida and Georgia. Leitneria pilosa differs from L. floridana in the presence of dense trichomes on both abaxial and adaxial leaf surfaces, while trichomes are sparse to absent on the leaf surfaces of L. floridana. Leaves of L. pilosa are smaller, about half the length, and have a lower length ∶ width ratio than leaves of L. floridana. Within L. pilosa, subsp. ozarkana indigenous to Arkansas and Missouri differs from subsp. pilosa indigenous to Texas by its consistently larger, elliptic to slightly oblanceolate or obovate leaves with longer petioles. Leaves of L. pilosa subsp. pilosa are narrower and lanceolate. These new taxonomic designations are supported strongly by data from molecular analyses and by the geographic disjunction of the taxa.