Theory predicts that edaphic endemics should exhibit high levels of population differentiation due to restricted gene flow among patchily distributed habitats. Here, we tested this prediction with the federally threatened annual Geocarpon minimum, an edaphic endemic restricted to sandstone outcrops and slick spots associated with saline prairies in the Southeastern United States. We used AFLP data to quantify population genetic variation and structure in 13 G. minimum populations using a bulked sampling scheme. Modest but significant components of genetic variance are partitioned among populations (16%) and among regions (north, south; 3%). The maintenance of private bands within most G. minimum populations suggests limited gene flow among geographically isolated populations. However, a Mantel test failed to detect a pattern of isolation by distance. Estimates of within population variation in G. minimum are relatively low compared to other edaphic endemics with similar life-histories. Results suggest conservation efforts should focus on protecting genetically unique populations and ensuring that genetic variability is adequately captured in ex situ collections.

Assessing border properties within vegetative assemblages is critical to the understanding of plant community dynamics and to the development of non-native species management protocols. Population border zones are the most dynamic part of a plant community and can be evaluated to determine population dynamics, management necessity, or species/species interactions. From a management perspective, changes in these borders can be used to evaluate the overall trajectory for populations in a community, the effects of disturbance, and/or non-native species on the community structure. We examined the trends of Artemisia vulgaris (L.) borders that were adjacent to other species populations in a mixed urban plant community in an effort to determine the future community identity and how interactions may vary among species of differing guilds. We analyzed trends in border properties, which were developed specifically for this study, over a four-year period. Our design included all co-dominant species bordering A. vulgaris from the following guilds: (1) Forbs, (2) Grasses, and (3) Shrubs resulting in a complete assessment of guild interactions (forb/forb, forb/grass, and forb/shrub). We found that interactions among species varied considerably and were not directly related to the guild membership. Instead, interactions and the dynamic nature of population borders varied on a species by species basis. Our results also suggest that population dynamics of differing life form guilds (i.e., forb/shrub) were not necessarily related to direct competitive interactions; rather, they may be a result of yearly fluctuations in the larger species' (shrub) population. Finally, we found that A. vulgaris did not necessarily exclude all species; in fact, A. vulgaris was thwarted by some species and co-mingled with others.

Dune ecosystems along the Great Lakes shoreline provide essential habitat for specialized plant communities and several state and federal listed rare species. I conducted a vegetation survey in Grand Sable Dunes, Pictured Rocks National Lakeshore, MI, in an effort to investigate the hypothesis that physical dune characteristics influence the distribution of encountered listed species of concern. Three species with concern status were encountered (Cirsium pitcheri, Stellaria longipes, and Tanacetum bipinnatum). Overall plant diversity was negatively correlated with soil pH. Increases in dune aspect and slope resulted in increased abundance of C. pitcheri and S. longipes, while T. bipinnatum decreased in abundance. Increases in species richness and plant density resulted in decreased abundance of C. pitcheri and T. bipinnatum, while S. longipes increased in abundance. These three species rarely co-occurred in quadrats. The gradient of dune stabilization that has naturally occurred within Grand Sable Dunes provides the necessary range of distinct microhabitat necessary for C. pitcheri, S. longipes, and T. bipinnatum to establish and maintain populations. Younger foredunes with less vegetation cover are necessary for C. pitcheri and T. bipinnatum. As dunes stabilize and more species colonize, the microhabitat becomes more suitable for S. longipes. Ensuring a natural range of dune stabilization from active foredunes to stable hind dunes will benefit conservation of endangered, threatened, and species of concern.

We synthesized the current information on mesophytic cove forests in the southern Appalachians, assessed the range of variation in herb species composition and diversity in stands with different disturbance histories and environmental conditions, identified key knowledge gaps, and suggested approaches to fill these knowledge gaps. The purpose of this synthesis was to provide information to forest managers to help make decisions about conservation assessments and strategies for rich cove forests in the southern Appalachians. An important finding is that no single study or data set can provide conclusive evidence or clear management strategies. However, an overriding conclusion is that the magnitude of impact and the management actions necessary to restore herbaceous communities are directly proportional to the severity of disturbance, current condition (e.g., presence of Rhododendron), site heterogeneity, and historical land use (e.g., agricultural activity). These factors plus a host of other stressors (e.g., climate variability, air pollution, invasives) are likely to have a strong influence on the highly variable patterns observed when comparing herbaceous diversity of ‘old-growth’ or uncut forests to human disturbed forests (e.g., cutting, air pollution, conversion, invasive plants or insects). Results from this review reinforce our premise that factors controlling herbaceous species presence and abundance are highly complex, thus broad generalizations about the impacts of a single factor such as logging should be interpreted with caution. Of the stressors known to affect forest trees (e.g., pests and pathogens, acidic deposition, air pollution, drought, and wind), little to no information exists on how these same stressors will affect herbaceous plants. A limited number of studies have examined the demography or physiology of forest herbs, particularly across all life stages. While the demography of a few genera have been studied (e.g., Hexastylis, Asarum, Trillium, Arisaema, Goodyera, Hepatica), little to no information exists for the majority of woodland herbs. Species identity is important when considering management of rich cove forests. Diversity may increase following canopy disturbances that favor recruitment of early-seral herbaceous species; therefore, simple indices of diversity (H′, S, and E) are not the best measure of recovery in mesophytic rich coves, particularly where shade-adapted ‘rich-cove indicator’ species have been replaced by these species. Species-specific life histories and the influence of prevailing site conditions are important lines of research for understanding recovery and sustainability of mesophytic rich cove forests.

In order to assess the effects of age on flooding tolerance, we conducted a mesocosm flooding experiment that examined biomass accumulation of two age cohorts of Xanthium strumarium L. We also examined repeated measures of stem height and diameter of each cohort for the duration of the experiment. We hypothesized that change in biomass measures (root and shoot biomass, increase in total biomass, and root shoot ratio) of older individuals would be greater than younger individuals under simulated flooded conditions. We further hypothesized that older individuals would be impacted more than younger individuals regarding stress; i.e., the younger cohort would acclimate and thus flooding effects would be masked. Results indicate that older individuals were more impacted by flooding than younger individuals for all biomass parameters. Height repeated measures indicated that older individuals differentially responded to flooding stress, compared to younger individuals; which was also the case for diameter repeated measures. Our study indicates that individuals exposed to flooding at an early age could be plastically developing acclimation structures leading to younger cohorts subsequently outperforming their older cohorts that did not develop under the stressed conditions.

In response to hurricane and oil-spill environmental impacts along the northern Gulf of Mexico, coastal and marine habitat restoration has become a priority. In particular, restoration of submerged aquatic plants is vital for ecosystem health. To facilitate restoration, developing propagation protocols for Gulf coast plants is necessary, but challenging due to the lack of information on many species. Previous seed germination research of Vallisneria americana, a submerged aquatic species with declining abundance in coastal habitats, from northern latitudinal populations reported germination percentages between 80–90%. Germination experiments using Mississippi Gulf coast plants revealed unexpected outcomes. Less than 8% germination occurred when seeds were germinated in a 16 hr photoperiod or 24 hr dark period at 10, 20, 30 or 40 °C. To enhance germination, cold stratification and gibberellic acid soak treatments were conducted, but germination was below 10%. A subsequent seed scarification experiment was conducted that resulted in 90% germination when incubated at 30 °C. In addition, an imbibition experiment revealed that both scarified and non-scarified seeds imbibed water. Due to this imbibition, V. americana seeds used in this study were considered to be physiologically dormant. Refining existing seed-based propagation protocols is recommended to ensure the success of revegetation in restoration projects.

A new species from Panama, Malaxis panamensis, is described and illustrated. So far this orchid is known exclusively from the Panamanian Cordillera Central. Malaxis panamensis seems to be related to M. woodsonii but the species are easily distinguished by the lip form.

Twenty noteworthy species of vascular plants are reported from the Torrey Range, encompassing southeastern New York, northern New Jersey, and southwestern Connecticut: Actinidia arguta, Carex kobomugi, C. merritt-fernaldii, Crocanthemum propinquum, Cyperus acuminatus, C. difformis, C. echinatus, C. pseudovegetus, Euphorbia serpens, Geum vernum, Hedeoma hispida, Hydrangea paniculata, Hydrocharis morsus-ranae, Juncus diffusissimus, Kalopanax septemlobus, Muhlenbergia asperifolia, Rotala ramosior, Scirpus pallidus, Tripidium ravennae, and Viola bicolor.