Little is known about interactions between shellfish and Alexandrium monilatum (Howell) Balech, a toxigenic dinoflagellate that forms blooms mostly in the Gulf of Mexico. Toxic A. monilatum produces endotoxins with hemolytic and neurotoxic properties, and has been linked to major fish and invertebrate kills. The responses of three ecologically important shellfish species to A. monilatum (toxic strain AMO3) were experimentally assessed. In the first set of experiments, grazing studies were conducted with adult and juvenile eastern oysters (Crassostrea virginica Gmelin), northern quahogs (Mercenaria mercenaria Linnaeus), and green mussels (Perna viridis Linnaeus), which inhabit areas where A. monilatum blooms occur. Clearance rates of each shellfish species were depressed when exposed to toxic A. monilatum (bloom density of ~550 cells ml-1) alone or with nontoxic Instant Algae® Pavlova, in comparison to clearance rates of control animals fed benign cryptophyte algae. There was also a reduction in the clearance rate of adult and juvenile C. virginica and P. viridis, as well as juvenile M. mercenaria exposed to A. monilatum, in comparison to control animals that were exposed to a nontoxic strain of a dinoflagellate of similar size, Alexandrium tamarense (clone CCMP115). Exposure to toxic A. monilatum significantly decreased shellfish valve gape in adult P. viridis and C. virginica. Intact A. monilatum cells were found within shellfish feces, but A. monilatum cells did not divide following passage through the gut. In the second set of experiments, survival of larval M. mercenaria and C. virginica was tested when the larvae were exposed to A. monilatum as intact cells, cells held in dialysis tubing, or sonicated cells. Survival of larvae was significantly less when exposed to sonicated A. monilatum, in comparison to survival of control larvae that were tested with nontoxic A. tamarense. Overall, these data indicate that A. monilatum blooms can adversely affect survival of some shellfish species by reducing clearance rate and valve gape, affecting food intake, and inducing larval mortality.

Echinacea laevigata (Boynton and Beadle) Blake, a federally endangered species, occurs in several small, isolated populations and a single large population in the northern Piedmont of North Carolina. Currently, little is known of the reproductive biology of this species. Therefore, we sought to describe its flowering phenology, compatibility pattern, and which of its various flower visitors were the more effective pollinators, to inform conservation efforts. In addition, pollinator limitation can reduce seed number and seed quality in small, isolated plant populations. We conducted a study of insect flower visitation and seed production in these populations to test our hypothesis that plants in the small, isolated populations are visited by fewer insect taxa, receive fewer visits, and produce fewer and/or less fit seeds than do plants in the large population. Our data show that average insect visitor species richness was significantly greater in the large population than in small populations and all but one of the small populations had fewer pollinator visits per head during fifteen minute observations than the large population; however, plants in several small populations produced as many or more seeds per head than did plants in the large population. Therefore, our results were not consistent with expectations of pollinator limitation. However, results show that seeds from small populations produce seedlings that are less fit as those from the large population. We conclude that other factors not examined in this study are more threatening to small, isolated coneflower populations than is pollinator limitation.

Sediments from the Late Cretaceous Tar Heel Formation in the Atlantic Coastal Plain of North Carolina were investigated for occurrence and distribution of palynomorphs. Exposures along rivers at Elizabethtown, Goldsboro, Ivanhoe, Lock, Willis Creek and Tar River in North Carolina were systematically collected. One hundred and three sediment samples were macerated by standard techniques modified by eliminating treatments with nitric acid and potassium hydroxide, and analyzed for palynomorphs. Eighty species of palynomorphs were distributed in 4 form genera of freshwater algae, 3 of dinoflagellates, 9 of fungi, 15 of pteridophytes, 11 of gymnosperms and 24 of angiosperms. Angiosperms were the dominant components in assemblages at all localities. Representatives of the Normapolles pollen group (characteristic angiosperm pollen group of middle and high northern latitudes of eastern North America and Europe) occur throughout the Tar Heel Formation and collectively comprise 29%-54% of the angiosperm assemblages. Palynological age assessment is in concordance with earlier dating determined by other workers based on invertebrate faunas. Minimum variance clustering with squared Euclidean distances in the Q-mode (clustering of samples) indicates that stratigraphically older layers of Ivanhoe, Lock and Willis Creek are similar in palynofloral composition, and one section of the Goldsboro locality is compositionally equivalent to the Tar River locality. Minimum variance cluster analysis in the R-mode (clustering of taxa) indicates the association of Campanian taxa in the same cluster. This reconfirms that localities of the Tar Heel Formation are of Early Campanian age. Informal biostratigraphic zones of Campanian (CA2-CA4) known from other Atlantic Coastal Plain deposits do not occur in the Tar Heel Formation. Quantitative analysis is consistent with the long-standing hypothesis of diversification and dominance of angiosperm pollen groups during the Campanian. The palynological record of the Tar Heel Formation, based on some indicator taxa with modern equivalents, suggests that subtropical to warm, moist temperate conditions prevailed in the southeastern region of North America during Campanian time.

Fire is a natural component of most terrestrial ecosystems and can act as a local wound stimulus to plants. The ultimate goal of this work was to characterize the array of transcripts which systemically accumulate in plants after fire damage. Before this could be accomplished, substantial development of methods for gene expression analysis using sequence data was necessary. This involved developing methods for identifying contamination in DNA sequence data (Chapter 2), identifying over 78,000 false sequences in GenBank and several thousand more in the indica rice genome (Chapter 2), developing a novel method for identifying housekeeping controls using sequence data (Chapter 3), performing relative expression analyses for 127 potential housekeeping control transcripts (Chapter 3), and characterizing 23 transcripts which encode all 13 subunits of vacuolar H+-ATPases in tomato plants (Chapter 4). A subtractive cDNA library served as a starting point to identify and characterize 9 novel tomato transcripts systemically up-regulated in leaves in the first hour after a distant leaf is flame wounded (Chapters 5). Real-time RT-PCR using leaf RNA isolated at different times after flaming showed that the most common pattern of transcript accumulation was an increase within 30 to 60 minutes, followed by a return to basal levels within 3 hours. Expression analyses also showed that most up-regulated transcripts were already present in unwounded tissues. A total of 46 different transcripts were identified from the subtractive cDNA library (Chapters 6). Compared with the entire tomato transcriptome, these 46 transcripts are very highly conserved in plants. The vast majority fell into 5 classes: enzymes of general metabolism; protein synthesis, modification, and transport; transcription; membrane transport; and photosynthesis and respiration. At least half of the transcripts have been previously associated with wounding or stress, suggesting that the systemic response to fire damage has components similar to those of other wound and stress responses. On the other hand, 30% of transcripts were associated with photosynthesis and respiration, suggesting that part of the response to fire damage is notably different from other wound and stress responses. Conclusions and future directions are included in Chapter 7.

Modulation of cytosolic calcium levels in both plants and animals is achieved by a system of Ca2+ -transport and storage pathways that include Ca2+ buffering proteins in the lumen of intracellular compartments. We used a transgenic approach to modulate calcium stores in the lumen of the endoplasmic reticulum in plants. We were able to use the low affinity, high capacity Ca2+ binding characteristics of the C-domain of calreticulin (CRT) to selectively increase Ca2+ storage in the endoplasmic reticulum, and to determine if those alterations affected plant physiological responses to stress. I fused the CRT C-domain to the C-terminal portion of the green fluorescent protein (GFP) and obtained transgenic plants that expressed high levels of the GFP-CRT C-domain fusion protein in the ER. I showed that this fusion protein was able to bind Ca2+ in vitro. These plants had increased Ca2+ stores in the ER and the ER calcium stores were used by the plant in times of calcium stress. The transformed seedlings also showed delayed loss of chlorophyll after transfer to high salt medium. The data suggest that expression of this calcium binding protein not only has the ability to increase bioavailable calcium stores but that the ER Ca2+ stores are important for plants to relieve the effect of salt stress. In the process of developing the transgenic plants, I also developed an array of other tools for subcellular localization, and targeting of the C-domain to various subcellular organelles. With two other colleagues, we also developed a GFP imaging system using the onion epidermal cells for visualizing subcellular localization of GFP and GFP fusion proteins.

Higher temperatures under climate change are likely to result in greater evaporation and increased soil moisture deficits. Increased drought will likely cause a shift in the vegetation distribution. This study focused on woody plants of the Southeastern United States mixed forest. Although water is not a primary limiting factor in this forest, species distribution suggests that water availability exerts a strong control on the success of woody plants. I used a comparative approach to understand environmental factors and corresponding species traits that determine species composition across a gradient of water availability. I compared hydraulic architecture, vulnerability to cavitation, and the ability of xeric and mesic species to germinate, grow and survive under varying levels of water stress. Congeneric pairs composed of one xeric and one mesic species were used. Seeds were subjected to polyethylene glycol solutions of different water potentials to compare the effects of water availability on germination of xeric and mesic species. I used understory saplings to compare the difference in the xylem hydraulic properties between xeric and mesic species and the air-injection method was used to determine differences in their xylem vulnerability to cavitation. I performed a dry-down experiment to compare the ability of the xeric and mesic species to survive extreme drought by evaluating survival after re-watering subsequent to drought exposure. Growth performance was evaluated by measuring electron transport rate (ETR), stomatal conductance (gs), shoot and root biomass of seedlings that were exposed to different levels of water (well-watered, dry, and flooded) and nutrients (high and low). Results indicate that the ability to germinate under drought did not differ consistently between xeric and mesic species, but, germination ability under drought was associated with the ability to maintain turgor. Stems of xeric species were less vulnerable to wilting than mesic species under drought stress. I found greater resistance to xylem cavitation in xeric species than mesic species. It appears that cavitation resistance was independent of specific conductivity and wood density since I did not find any trade-off between specific conductivity and vulnerability to cavitation among the woody plants examined. In the growth performance study, xeric species tend to have lower whole plant biomass, higher Root:Shoot (R/S) ratio, higher coarse root mass ratio (CRMR) and less reduction in gs under drought stress than mesic species. The higher stomatal conductance and lower photorespiration rates among the mesic species may have influenced their increased photosynthetic rates, thereby producing a greater total plant biomass than xeric species. Species distribution along water availability gradients appears to be better explained by the ability of seedlings to resist cavitation, to tolerate and survive water stress, and by their biomass allocation patterns, rather than by their ability to germinate under drought.

The ecological significance of montane non-alluvial wetlands in the southern Blue Ridge region of North Carolina is well known. However, there is relatively little quantitative documentation of these community types. In particular, our understanding of montane, peat-forming wetlands is based primarily on qualitative data, and there has been no previous comprehensive classification and description of these community types. In this study, species composition and vegetation-environment relationships are described for the geographically-isolated, non-alluvial wetlands of the southern Blue Ridge region of North Carolina. A hierarchical classification is presented for 12 community types within 2 broad vegetation classes based on 136 vegetation plots spanning the range of the southern Blue Ridge region of North Carolina. Hierarchical cluster analysis was used to delimit community types, and non-metric multidimensional scaling was subsequently used to help differentiate the community types identified by the cluster analysis. Although some of these community types fit well within currently recognized community concepts, others fit poorly within existing concepts, pointing to a need for definition of new types and/or significant refinement of types currently recognized. The 2 broad vegetation classes and 12 community types are discussed, each with a description of composition, related community concepts, and environmental context. Compositional variation among the types is most strongly associated with elevation, soil pH, soil nutrient availability, and soil cation exchange capacity.

The interactions between conifers, bark beetles and their common fungal associates have been widely studied, in part due to the severe economic and natural losses that occur annually. Host resistance, involving constitutive and induced defensive measures, and the factors associated with pest success are now widely understood and some losses can be avoided with proper management. Recent research with Norway spruce (Picea abies) has provided additional insight into the chemical pathways involved in host resistance, and has determined that trees exposed to mechanical wounding or fungal inoculation show acquired resistance to future pathogen attacks. This aspect of defense in loblolly pine (Pinus taeda) has not been adequately investigated. However, our recent studies indicate that fungal inoculation results in elevated resin flow levels that last up to one year after treatment. Further research in southern Appalachian pines showed that elevated resin flow occurs in response to low intensity fire, and that this response is still present at 18 months after burning. These studies indicate that acquired resistance through induced resin flow in southern pines is a possibility. Further research with beetle or fungal challenges could determine new possibilities for management of both natural and planted stands in order to maximize host defenses against southern pine beetle.

A Review of manuscripts written by European explorers and colonists affords the opportunity to develop a clearer understanding both of types of plants employed and their significance in religion and medicine during the 16th to 19th centuries. This paper is a distillation of accounts by thirteen European explorers, written between 1545 until 1861, about Laos and the Lao people in Siam. All of the references to plants and plant use have been extracted for an analysis of which plants European explorers viewed being used traditionally in Laos during this time period and information on how these plants were used and collected. Many of the plants described in the texts were medicinal in nature and some have been examined for modern pharmaceutical use. These pharmaceutical studies have substantiated the effectiveness of historical medicinal plant use. The texts also describe plants that were used in religious ceremonies and that continue to play an important role in Lao culture. Future comparative analysis of these early records with modern day observations of plant use should prove productive in formulating assessments of Traditional Environmental Knowledge loss and the impact of this loss on daily life. Understanding the plants that are important to native Lao in the past can lead to better methods of conservation in the future.

The goal of this research was to build upon present understanding of the eutrophication process in the Neuse Estuary ecosystem by evaluating linkages among land use practices, nutrient concentrations and ratios, and phytoplankton assemblage composition. First, geographic Information Systems (GIS) analysis was used to characterize 26 sub-basins throughout the Neuse watershed for changes in land use over the past decade. GIS was also used in concert with multivariate statistics to synthesize and integrate ten years of land cover and water quality data into a conceptual model. Second, a continuous, decadal record of the phytoplankton in the mesohaline Neuse Estuary, in conjunction with synoptic measurement of environmental variables, provided a unique opportunity to evaluate responses of the phytoplankton assemblages to changing environmental conditions. Ordination techniques were used to investigate potential environmental predictors of phytoplankton community patterns through the process of eutrophication. Analyses indicated that over the past 10 years, total phosphorus concentrations were significantly higher during summer months in sub-watersheds with high densities of wastewater treatment plants (WWTPs) and confined swine feed operations. Nitrate concentrations were significantly higher during winter in sub-watersheds with high WWTP densities, and both inorganic and organic forms of nitrogen were significantly higher in sub-watersheds with greater agricultural land use. Ammonium concentrations were significantly higher after high-precipitation periods, but were not significantly correlated with the land-use parameters included in this study. In the Neuse Estuary, among several important findings, abundance of the potentially toxic, bloom-forming dinoflagellate Prorocentrum minimum was positively related to low water temperatures (winter/spring) and organic nitrogen and suspended solids concentrations. In addition, abundance of other potentially toxic flagellated algae such as the raphidophyte, Heterosigma akashiwo, has increased over the past decade, and H. akashiwo was found to be an ?indicator species? for high ammonium concentrations (> 50 μg/L). Overall, the data indicate that wastewater discharges in the upper Neuse basin and intensive swine agriculture in the lower basin have been the highest contributors of nitrogen and phosphorus to receiving surface waters. In the estuary, increased nutrients, especially ammonium, are promoting increased abundance of several potentially toxic, bloom-forming phytoplankton species.