Botany Commons^™

The Influences Of Disperser Behavior, Host Availability, And Environmental Conditions On The Distribution Of Oak Mistletoe [Phoradendron Leucarpum (Raf.) Reveal & M. C. Johnst.] In Eastern Virginia And North Carolina, Nicholas Pearce Flanders

Biological Sciences Theses & Dissertations

Mistletoes are shrubs that typically parasitize the branches of host trees and rely on avian frugivores for seed dispersal. Because mistletoes are restricted to a narrow range of suitable recruitment sites and avian frugivores are more visible than other guilds of seed dispersers, mistletoe-frugivore systems afford opportunities for assessing the roles of dispersal limitation and local environment in determining plant distribution. These mechanisms have been proposed as determinants of the observed association of oak mistletoe [Phoradendron leucarpum (Raf.) Reveal & M. C. Johnst.] with forested wetlands in eastern Virginia and North Carolina, USA. I tested the alternative hypothesis that …

Temporal Dynamics And Seed Dispersal In Plant-Frugivore Communities Of The Dominican Republic, Spencer Christian Schubert

Biological Sciences Theses & Dissertations

Plant-animal mutualisms are a foundational component of biodiversity in terrestrial ecosystems. Most tropical forest plants have adapted to produce fleshy fruits to attract frugivorous animals to disperse seeds. Interaction patterns among plant taxa and their seed dispersers are driven by a complex suite of factors involving their evolutionary history and environmental context, and the structure of these mutualistic networks are theoretically tied to their ecological function. I carried out a series of field studies to investigate the temporal dynamics of mutualistic interactions of plant and avian frugivore communities in the central Dominican Republic and how their characteristics affect seed dispersal …

Molecular Systematics Of Isoëtes (Isoëtaceae) In Eastern North America, Peter William Schafran

Biological Sciences Theses & Dissertations

Isoëtes (Isoëtaceae, Isoetales, Lycopodiophyta) is a cosmopolitan genus of aquatic lycophytes, occurring on every continent except Antarctica. Of approximately 200 total taxa, about half are in a clade of species mostly occurring in North and South America. Eastern North America accounts for 22% of global taxonomic diversity, containing 32 fertile taxa and 16 named hybrids. This taxonomic diversity is built upon relatively little morphological difference, and even combined with phylogenetic analysis using several nuclear and chloroplast DNA markers, no well-resolved systematic treatment within this clade exists.

This study aims to clarify the relationships between all species and subspecies of Isoëtes …

Foraging Behavior Of Spring Bees And Their Agricultural Implications, Michael D. Gregory

Biological Sciences Theses & Dissertations

Colony Collapse Disorder has greatly reduced honey bee populations in the last decade. Native bees have been largely neglected in research, and their floral preferences may have agricultural implications because native bees ameliorate the demand to rely solely on non-native bees. In this work, pollinator visitation to flowers with manipulated ultraviolet floral patterns was monitored. Populations of wild showy golden-eye in Colorado, plus cultivar populations of black-eyed Susan and lawn populations of buttercups in Virginia were monitored for pollinator landings to compare preference for unmanipulated ultraviolet-absorptive floral guide preferences. Another number, a proxy for pollen load, was manipulated on strawberry …

Groundwater Thresholds For Root Decomposition And The Relation To Barrier Island Ecological State Changes, Matthew Lee Smith

Biological Sciences Theses & Dissertations

Barrier islands off the eastern shore of Virginia exhibit distinct habitats that abruptly transition between periodically brackish/freshwater marshes, wooded swales, and sparsely vegetated dunes. There is strong evidence that the plant communities and ecosystem processes occurring in each habitat are primarily influenced by nutrient availability and the distance between two of the three free surfaces: land and freshwater. At the Virginia Coast Reserve-Long Term Ecological Research Site in Virginia, USA, thresholds to belowground decomposition rates were identified by measuring decay of native roots and rhizomes at 32 elevations in relation to mean annual groundwater levels (-0.356 – 1.937 m). Negative …

Molecular Phylogeny Of The Genus Houstonia And Allies In Rubiaceae, Hunter Lee Shanks

Biological Sciences Theses & Dissertations

Houstonia (Rubiaceae) is a strictly North American genus of 24 species distributed from Mexico, throughout the United States, up to Canada. Houstonia has proven to be a taxonomically difficult genus since the Linnaean description of Houstonia and the related genera: Hedyotis and Oldenlandia in 1753. For over 250 years botanists have lumped and separated Houstonia from Hedyotis and Oldenlandia based on various morphological characters. The most recent circumscription of Houstonia (Terrell 1996) separated the genus into two subgenera with each subgenus containing two sections. Nuclear (ITS) and plastid (trnL-F, rps16) DNA sequences were used to build a molecular phylogeny depicting …

Molecular Phylogenetics And Historical Biogeography Of The Tribe Chiococceae (Rubiaceae), Sushil Kumar Paudyal

Biological Sciences Theses & Dissertations

Chiococceae are a monophyletic assemblage of morphologically very diverse groups of plants ranging in habit from subshrubs to shrubs to tall trees exhibiting an astonishing variation in shapes and sizes of corolla, and kinds of fruits and seeds. They are primarily distributed in the Neotropics but also occur in the West Pacific islands; thus exhibiting amphi-Pacific tropical disjunction. This study addresses the phylogenetic relationships and biogeography of the Chiococceae using molecular DNA sequence data, and presents novel data on the tribal and generic delimitations, intergeneric relationships, and the origin and dispersal of this group.

In the most recent tribal delimitations …

A Molecular Framework Phylogeny For Ptilotus (Amaranthaceae), Timothy A. Hammer

Biological Sciences Theses & Dissertations

Ptilotus (Amaranthaceae) is an Australian genus with over 100 species, most of which occur in arid Western Australia. Ptilotus has been a taxonomically difficult genus; despite rigorous morphological studies into the genus over many years, previous workers have found it difficult to delimit infrageneric groups due to inconsistent morphological variation. With the goal to establish a phylogenetic framework for the genus, 100 taxa were sampled, including 87 Ptilotus spp., and the ITS nrDNA and matK cpDNA were sequenced. The phylogeny was reconstructed using Bayesian, maximum likelihood and maximum parsimony analyses on separate and concatenated datasets. Morphological characters were assessed and …

The Ethnobotany Of Pistacia Eurycarpa Yalt. In Iraqi-Kurdistan: Its Uses, Chemical Composition, And Anti-Biotic Activity Of Its Resin, Peter W. Schafran

Biological Sciences Theses & Dissertations

Pistacia eurycarpa Yalt. is a wild relative of pistachio (P. vera L.} that grows in the Zagros Mountains. For the Kurds who inhabit these mountains the tree has practical and cultural applications. All parts of this tree have a use, for structural materials, food, and medicine. While weII known in this region, the ethnobotany of P. eurycarpa is unknown in the outside world. I spent May and June of 2011 - 2013 in Sulaimani, Kurdistan, Iraq, collecting information on this tree. In this time period I was able to witness the harvest of unripe fruits. Information about the tree …

Evolution On The Hawaiian Hotspot: Biogeography And Divergence Time Estimation Of Kadua (Rubiaceae), Kenneth L. Parker

Biological Sciences Theses & Dissertations

Recent studies on the colonization time of Hawaiian plant and animal lineages have suggested certain lineages arrived to the archipelago before the formation of the extant islands. Kadua, a recently resurrected genus, is mostly endemic to the Hawaiian Archipelago, with many member taxa autochthonous to individual islands. This work investigates the colonization time of Kadua to the Hawaiian Islands. Sequence analyses of the quickly evolving nuclear regions ITS, ETS and 5s-NTS regions for 20 Hawaiian and 7 French Polynesian species of Kadua were used to create dated phylogeny calibrated with island ages. The phylogeny suggests a single colonization of Hawaii …

Ecological And Genetic Status Of The Purple Pitcher Plant, Sarracenia Purpurea L., In Maryland And Virginia, Philip M. Sheridan

Biological Sciences Theses & Dissertations

Sarracenia purpurea is a rare wetland plant in Virginia and a threatened species in Maryland, with two potential subspecies in the region. I utilized restriction fragments from the intron of the chalcone synthase gene to compare S. purpurea populations and determine whether the subspecies concept was supported. I performed a census of existing populations, compiled all known historical data on the species, and investigated the reasons for the species demise and predicted dates of extinction. Bloom phenology was examined to see if climate change may have influenced bloom period. Soil, vegetation, and climatic information was obtained to determine if taxonomic …

Interisland Variability Of Dune Plant Community Structure On Virginia's Barrier Islands, Justin K. Shafer

Biological Sciences Theses & Dissertations

The barrier islands of the Virginia Coast Reserve LTER site provide an opportunity to study interisland variability of dune plant communities. My research focused on the variation in biomass and diversity of communities among islands and dune positions. Grassy dunes of young, intermediate and old age were sampled on Smith, Hog, and Parramore Islands. Aboveground biomass was obtained from harvest plots, and roots were extracted from cores. Data were collected on depth to groundwater and total soil nitrogen. Variation in mean aboveground biomass was evident among the islands with the highest values on Hog Island, followed by Smith, then Parramore …

Ecology And Molecular Phylogenetics Of Hydnora (Hydnoraceae) In Southern Africa, Jay Francis Bolin

Biological Sciences Theses & Dissertations

The Hydnoraceae are a clade of root holoparasitic angiosperms that contain two small genera, Hydnora and Prosopanche. This study, focused on Hydnora, presents novel data regarding the pollination biology, germination ecology, parasite-host nutritional relationships, and the molecular systematics of this group. Experimental addition of the primary pollinator, Dermestes maculatus to Hydnora africana chamber flowers demonstrated beetle imprisonment during the carpellate stage. Changes in the inner surfaces of the androecial chamber allowed beetle escape after pollen release. Most beetles escaped, dusted with viable pollen, three days after pollen release. To investigate germination ecology, aqueous root extracts of host and …

Microspore Wall Morphogenesis And Orbicule Ultrastructure Of Isoetes, Khalid Alarid

Biological Sciences Theses & Dissertations

The microspore wall morphogenesis and orbicule ultrastructure of Isoetes were studied using electron microscopy. Microspore wall morphogenesis in five species of Isoetes (I. appalachiana, I. engelmannii, I. hyemalis, I. piedmontana, and an undescribed species from York Co., VA, USA) was studied using scanning and transmission electron microscopy. Results show that they generally have the same developmental stages in terms of microspore wall morphogenesis. The mature microspore wall consisted of four layers: perispore, paraexospore, exospore and endospore. Paraexospore formation began during the tetrad stage. The exospore was then formed between the paraexospore and the plasma membrane. During the free spore …

Plant Assemblage Structure On Barrier Island ‘Pimple’ Dunes At The Virginia Coast Reserve Long-Term Ecological Research Site, Brett A. Mcmillan

Biological Sciences Theses & Dissertations

The habitats at the VCR LTER that were the focus of the current study are the Hog Island and Parramore Island 'pimples', small, rounded dunes forming along main dune ridges of the barrier islands. There are distinct plant assemblage zones found on pimples, although most of these dunes are 10–20 m in diameter. Hypotheses of the study were that fresh water availability was a main determinant of differences between assemblages and that pimple size and location would influence diversity and assemblage structure. Research goals were (1) to describe the plant assemblages on pimples, (2) to relate edaphic and geomorphological factors …

Fine Root Vitality And Its Application In A Minirhizotron Study Of A Co2 Enrichment In A Florida Scrub Oak Ecosystem, Brandon Todd Herbert

Biological Sciences Theses & Dissertations

Minirhizotron images are assigned color codes to approximate the age of individual roots in situ. Triphenyl-tetrazolium chloride (TTC) has been used to measure the vitality of plant tissue by detecting dehydrogenase activity. TTC was used to assess the vitality of root tissue by color in a scrub oak ecosystem at Kennedy Space Center in central Florida. Roots were excavated, sorted into four color classes and stained with TTC. The product of the reduction of TTC by dehydrogenase enzyme, formazan, was extracted and its absorbance recorded using a spectrophotometer. A significant difference (p2 enrichment being conducted on a scrub oak …

Fine Root Dynamics In Atlantic White Cedar (Chamaecyparis Thyoides) Wetlands: Patterns Of Ecosystem Development In Natural And Restoration Settings, Harvey Leroy Rodgers

Biological Sciences Theses & Dissertations

This work addresses seasonal and successional factors of root dynamics in natural and restoration Atlantic white cedar (AWC) wetlands. Using minirhizotrons, fine root dynamics in a chronosequence of naturally-regenerating and restoration AWC wetlands were measured to compare ecosystem development trends with restoration conditions. A second study was conducted to compare fine root dynamics in AWC wetlands with contrasting hydroperiods. In addition, a technical study was conducted to determine the feasibility of estimating root biomass with indirect minirhizotron measurements.

Root biomass estimates using minirhizotrons were significantly higher in naturally regenerating AWC wetlands and significantly lower in the restoration site relative to …

The Effect Of Nitrogen Fertilization On Short-Term Fine Root Dynamics In A Barrier Island Dune Community, John Walter Hutton

Biological Sciences Theses & Dissertations

Fine root dynamics are an important yet poorly understood component of terrestrial ecosystems. In recent years a number of researchers have focused on fine root dynamics; their work has looked at patterns across one or multiple growing seasons on a scale of monthly measures. The purpose of this study was to add to the overall understanding by looking at fine root dynamics on a shorter temporal scale. Minirhizotron observation tubes were used to assess the effect of nitrogen fertilization on short-term fine root dynamics in a nutrient limited, barrier island dune system. Root length elongation and mortality rates followed expected …

Effects Of Elevated Atmospheric Co2 On Root Growth, Turnover And Decomposition In A Scrub Oak Ecosystem, John Joseph Dilustro

Biological Sciences Theses & Dissertations

Atmospheric carbon dioxide levels are increasing and predicted to double this century. The implications of this rise on vegetation structure and function are not well understood. Measurement of root growth response to elevated atmospheric carbon dioxide is critical to understanding soil carbon input. I investigated the effects of elevated carbon dioxide on fine root growth and decomposition using open top chambers with both ambient and elevated (700 PPM) CO₂ treatments in an oak-palmetto scrub ecosystem at Kennedy Space Center, Florida. Minirhizotron tubes were installed in each elevated and control chamber to allow observation of roots. Each tube was sampled …

Studies On The Biology Of Striga Aspera (Scrophulariaceae) In Nigeria, Emmanuel Izaka Aigbokhan

Biological Sciences Theses & Dissertations

Studies on Striga aspera are few and little information exists on its relationship with the morphologically similar and much studied S. hermonthica. Both species are sympatric in West Africa and if they hybridize, may serve as virulent gene reservoirs for each other.

The primary focus of this study was on the biology of S. aspera in Nigeria. The research focussed on its distribution, phenology, cytology, hybridization, seed dormancy, viability and germination in relation to S. hermonthica. Related studies involving the hybrids include genetic and morphological variability, pathogenicity and the simultaneous dual infection of a maize plant by both species.

In …

Fine Root Biomass Distribution And Production Along A Barrier Island Chronosequence, Mark Jeffrey Stevenson

Biological Sciences Theses & Dissertations

Fine roots play an important role in community development on barrier islands. Fine roots can influence nutrient losses from the soil environment along with regulating water loss based on their distribution and concentration (Nobel et al., 1989; Gleeson and Tilman, 1990). A sequential coring method was used to determine fine root biomass and total biomass along a chronosequence of barrier island dunes and swales on the Virginia Coast Reserve - Long Term Ecological Research Site. Fine root production and the effects of nitrogen fertilization were also examined using an ingrowth core method along the chronosequence. Live fine root biomass, total …

The Effect Of Nitrogen Fertilization On The Phenology Of Roots In A Barrier Island Sand Dune Community, Everett P. Weber

Biological Sciences Theses & Dissertations

Little work has been done on the phenology of root growth and senescence largely due to methodological difficulties. The application of minirhizotron technology has enabled the tracking of individual roots through an entire growing season. As a result, direct measures of turnover, root growth, and an analysis of cohorts were made. Small plots on a 36 year old dune on Hog Island, a barrier island in the Virginia Coast Reserve Long Term Ecological Research Site, were fertilized with nitrogen. Minirhizotron tubes were installed in each fertilized and control plot. Each tube was sampled monthly for nine months, March through October …

Population Dynamics In Response To Fire In Quercus Laevis - Pinus Palustris Barrens And Related Communities In Southeast Virginia, Allen E. Plocher

Biological Sciences Theses & Dissertations

Permanent plots in the Zuni Pine Barrens (Isle of Wight Co., Virginia) were sampled in order to: quantify plant population dynamics in response to fire, compare these dynamics among different moisture regimes, compare the effect of mechanical understory removal to that of fire on tree seedling and herbaceous dynamics, and determine the effect of dense lichen (Cladonia spp.) coverage on pine seedling establishment and survival. Fire resulted in 40% aboveground mortality in the overstory, 80% in the sapling/large shrub layer, and nearly 100% in the understory, followed by a 3.3 to 10.6 fold increase in understory density. Regeneration …

Root Biomass And Production In Four Communities Within The Great Dismal Swamp, Susan West Powell

Biological Sciences Theses & Dissertations

A biomass difference approach was used to measure biomass and production over eleven months in four different communities within the Great Dismal Swamp. On all sites, fine roots were the moat dynamic root component. Both biomass and production were highest on the mixed hardwood site, the least flooded site, and second highest on the cedar site, the site with the longest duration of saturation. The maple-gum and cypress sites had lower amounts of biomass and rates of production. Environmental parameters that influenced production included frequency and duration of flooding, density of the stand, and soil type.

A second method, an …

An Autecological Study Of Pyxidanthera Barbulata In The Blackwater Ecologic Preserve Virginia, John Marc Lowenthal

Biological Sciences Theses & Dissertations

Pyxidanthera barbulata (pyxie moss), a rare and endangered subshrub, has been found in decreasing numbers in it's "pine barren" habitat. An autecological study encompassing vegetation association analysis and environmental measurements was performed in the Blackwater Ecologic Preserve, its only known location in Virginia. The preserve is being subjected to controlled burning and the effect of burning on the species was evaluated. A multivariate analysis of variance was performed to identify species associations, and simple analysis of variance was done to find trends in the environmental data. Four taxa were positively associated with P. barbulata, Gaultheria procumbens, Vaccinium tenellum, Cladonia spp., …

A Study Of Striga Chromosome Numbers With A Comparison To Those Of Some Genera In The Rhinathoideae And The Orobanchaceae, Cynthia White

Biological Sciences Theses & Dissertations

New chromosome counts are given for nine species of Striga including S. elegans (n=18), S. asiatica (n=19), S. forbesii (n=22), S. densiflora (n=26), S. aspera (n=27), S. passargei (n=28), and S. hermonthica (n=30). Previous counts reported for S. gesnerioides (n=20) and S. angustifolia (n=20) are verified. Evidence from the base number (x=10), chromosome counts, and differences in chromosome size (bimodality) suggests that the genus is an allotriploid with a descending aneuploid series. Genomic change appears to occur by different mechanisms in the Rhinanthoideae; some genera display a euploid series, others show aneuploidy, and some are very stable. Genera examined …

Decomposition Of Roots In The Great Dismal Swamp, Edward G. Tupacz

Biological Sciences Theses & Dissertations

The decomposition rates of roots to a depth of 40 cm were estimated by two methods in four plant communities in the periodically flooded Great Dismal Swamp. Modified litter bags and a core method were simultaneously employed on three flooded sites and an unflooded mixed hardwood site. Reciprocal samples (litter from each of the other sites) were placed on each site to examine the effects of litter composition.

For the litter bags, the cedar and maple - gum sites displayed the lowest mean decay rate. However, reciprocal samples showed that roots from the cedar and mixed hardwood sites decayed the …

Evaluation Of Two Methods For Estimating Belowground Production In The Great Dismal Swamp, Millie Symbula

Biological Sciences Theses & Dissertations

Two methods were used to estimate belowground production in a maple-gum stand in the seasonally flooded Great Dismal Swamp of Virginia. The first was an auger method which involved sequential core sampling. The second method was an implanted soil mass technique. Nylon mesh bags were filled with peat and buried at the study site. New growth into these implants was taken to be production.

Mean annual lateral root biomass and necromass to 40 cm, determined from soil cores, were 583 g·m^-2 and 281 g·m^-2, respectively. Production estimates for roots ≤ 5 mm in diameter, using soil cores, …

The Effect Of Pre-Sterile Medium Ph Photoperiod And N6-(2-Isopentenyl)-Adenine (2ip) On Shoot Production During Stage Ii Micropropagation Of Rhododendrons, Lori Longo Smith

Biological Sciences Theses & Dissertations

The number of shoots produced during a six week subculture of two Rhododendron sp., cultivars Rocket and Gibraltar was the same for both 16 and 24 hour photoperiods under cool white fluorescent lights, whereas significantly fewer shoots were produced under a 10 hour photoperiod for ‘Rocket.' Increasing concentrations of N₆- (2-isopentenyl)- adenine (2iP) from 0 to 32 μMin Anderson's medium resulted in proportional increases in shoot number. When shoots were cultured in the presence of indole-3-acetic acid (IAA) and 2iP, shoot multiplication was increased significantly over shoots cultured with 2iF alone. No interaction affecting shoot multiplication was …

Organic Matter Budgets And Models For Four Plant Communities In The Great Dismal Swamp, J. Patrick Megonigal

Biological Sciences Theses & Dissertations

Budgets and models of organic matter dynamics were developed for one mesic and three seasonally flooded plant communities in the Dismal Swamp. Components included aboveground parts, belowground parts, litter and soil organic matter (SOM).

Net primary- production was significantly greater on them flooded sites. Comparisons show that the Dismal Swamp is highly productive despite relatively low nutrient inputs.

Budget calculations showed that over 65% of the total input to SOM comes from roots. Leaves contributed about 70% of the aboveground inputs.

The model predicted that species composition, aboveground biomass and turnover rates on the cedar site will become quite similar …