Terrestrial and Aquatic Ecology Commons^™

Incomplete Denitrification In Thermus Species, Chrisabelle Mefferd

UNLV Theses, Dissertations, Professional Papers, and Capstones

Members the bacterial genus Thermus have been shown to be incomplete denitrifiers, terminating with nitrite or nitrous oxide (N2O). However, the ability to carry out denitrification and the evolution of nitrogen oxide reductase genes in Thermus remains poorly understood. This study tests the hypothesis that incomplete denitrification is common in Thermus and seeks to uncover patterns in the evolution of denitrification pathways in Thermus. Denitrification capacity was determined in a collection of 25 strains representing ten species of Thermus and phylogenetic analysis was performed to determine whether denitrification genes evolved horizontally in Thermus. No strains in this study reduced nitrate …

Assessing The Importance Of Nurse Plant Associations To The Growth Of Pre-~Reproductive Yucca Brevifolia, Eric James Chameroy

UNLV Theses, Dissertations, Professional Papers, and Capstones

Facilitation and competition among plant species, in addition to abiotic factors, play an important role in determining plant community structure in arid and semi-arid environments. I conducted a study in Dry Lake Valley, Lincoln County, Nevada, USA to investigate the importance of nurse plant associations to pre-reproductive Yucca brevifolia (Joshua tree). Dry Lake Valley lies within a transition desert between the Mojave and Great Basin Deserts with ecotonal plant communities consisting of species representative of both deserts. A vegetation survey described the communities in which this study was conducted as a Y. brevifolia woodland dominated by an understory of Ephedra …

Decontamination Protocols For Watercraft And Wildland Firefighting Equipment In Preventing The Spread Of Invasive Quagga (Dreissena Rostriformis Bugensis) And Zebra (Dreissena Polymorpha) Mussels, Ashlie Watters

UNLV Theses, Dissertations, Professional Papers, and Capstones

Quagga and zebra mussels (Dreissena rostriformis bugensis and Dreissena polymorpha) are two invasive species introduced via ballast water discharged by large oceanic cargo ships to the North American Great Lakes in the late 1980s. Once established, the mussels spread quickly. In January 2007, D. rostriformis bugensis was discovered in Lake Mead, NV-AZ, and in that same year, mussels were confirmed further south on the Colorado River in Lakes Mojave and Havasu. Dreissenids clog water intake pipes, water filtration systems, and electric generating plants. The mussels also ruin boat motors, damage recreational equipment, and once established in the reservoir, routine maintenance …

Prymnesium Parvum And Fish Kills In A Southern Nevada Man-~Made Reservoir, Tara Gregg

UNLV Theses, Dissertations, Professional Papers, and Capstones

The water chemistry of Lake Las Vegas (LLV), a Southern Nevada man-made reservoir, is influenced by both anthropogenic and natural sources. These sources affect the reservoir's water chemistry, which may promote harmful algal blooms (HABs) leading to massive fish kill events. Fish kills, caused by the golden algaePrymnesium parvum (P. parvum), continue to pose a threat in the reservoir. However, no effective treatments to controlP. parvumin large reservoirs such as LLV have been determined. This cross-sectional study evaluated important variables that may affectP. parvumHABs in LLV, including non-P. parvumbiomass (mg/m3), total zooplankton abundance (#/m3), temperature, TDS (salinity), mineral concentration (Ca, …

Pronghorn (Antilocapra Americana) Offspring Recruitment On The Carrizo Plain National Monument: Evaluating The Effects Of Low Population Density And Marginal Habitat Quality., Diego Ramirez Johnson

UNLV Theses, Dissertations, Professional Papers, and Capstones

Demographic fluctuation among ungulate populations is strongly linked to variability in recruitment. Rates of recruitment are subject to various forms of density-dependent and density-independent regulation. For species which benefit from the presence of conspecifics, reduced population density can decrease rates of recruitment and trigger a decline in per capita growth. Termed the Allee effect, this scenario can cause demographic collapse and population extinction. For many ungulate species, predation on juveniles is reduced when the timing and distribution of births is synchronized within a local population. Because birth synchrony is density-dependent, it may act as a mechanism for the Allee effect …

Understanding Basin Specific Life History Characteristics Of Lake Mead Quagga Mussels (Dreissena Bugensis) And A Potential Treatment Using Uv Radiation In Laboratory Studies, Melissa Thaw

UNLV Theses, Dissertations, Professional Papers, and Capstones

The quagga mussel (Dreissena bugensis) is an aquatic invasive species that is spreading throughout Lake Mead and other western waterways. Unlike their native waters in Eurasia, Lake Mead exhibits year round warm temperatures, high calcium levels and a lack of natural predators, all of which are very favorable conditions for their growth and spread. Dreissena bugensis reproduce and colonize hard surfaces rapidly, where they filter large amounts of water. They disrupt the aquatic food chain and interfere with infrastructure that is exposed to lake water. There is an urgent need to understand Dreissena bugensis life history characteristics within this new …

Dispersal Ecology Of Desert Mosses Along Gradients Of Elevation, Wildfire Disturbance And Local Niche, Robert Joseph Smith

UNLV Theses, Dissertations, Professional Papers, and Capstones

Much of the variation in plant communities can be explained by the dispersal of individuals across landscapes, an ecological process that contributes to clinal variation, post-disturbance recovery and habitat occupancy. The role of dispersal is of particular concern for Mojave Desert plant communities that may not be able to tolerate recent departures from historical fire regimes. The aim of this thesis was to infer how dispersal is reflected by patterns of diversity in disturbed and undisturbed bryophyte communities in the Spring Mountains of southern Nevada. Chapter 2 presents an examination of sub-surface bryophyte communities (propagule "soil-banks") along a 1400 m …

Understanding Effects Of Changes In Land Use, Environmental Parameters, Habitat Characteristics On The Great Basin Aquatic Invertebrates Using Ecological Stoichiometric Theory, Knut Mehler

UNLV Theses, Dissertations, Professional Papers, and Capstones

Many freshwater ecosystems in the Great Basin have undergone dramatic alteration over the past decades due to groundwater withdrawal, water diversion and changes in land use. These changes have affected benthic food web dynamics by altering the availability of chemical key elements for primary and secondary producers, by loss of biodiversity and extinction of endemic species. However, only few studies are available that addresses the link between changes in land use, habitat characteristics and its effects on benthic macroinvertebrates (BMI) communities comprehensively and little attention has been given to integrating physiochemical aspects to link ecosystem functions.

This dissertation analyzes the …

Dreissena Rostiformis Bugensis: Desiccation Of Adult Quagga Mussels Found In Lake Mead As A Preventive Measure Against Overland Dispersal In The Western United States, Matthew Kappel

UNLV Theses, Dissertations, Professional Papers, and Capstones

The expansion of civilization across all borders of the world has proven to affect major components of ecosystems. Since the introduction and establishment of the aquatic invasive species (AIS),Dreissena rostiformis bugensis, commonly known as the quagga mussel, into the United States there has been an extensive amount of time and money spent on controlling and preventing their expansion across the United States. The quagga mussel is of major concern because of its ability to disrupt the ecological communities in previously non-infested bodies of water, which may cause a loss in biodiversity and effect environmental health. The quagga mussel has spread …

Natural And Constructed Wetlands For Ecosystem And Engineering Services In The Arid And Semi-Arid Regions, Achyut Raj Adhikari

UNLV Theses, Dissertations, Professional Papers, and Capstones

The Las Vegas Wash (LVW) has undergone significant wetlands degradation and soil erosion over the past thirty years due to increasing flow resulting from urbanization and large rainfall events in the Las Vegas Valley Watershed. The increased flow and associated pollution load in the LVW and its adverse impact in Lake Mead have alerted stakeholders to pay a greater attention to explore alternative measures for rehabilitation of wetland ecosystems. This dissertation, using the case of changes in LVW, analyzes and describes ecological and engineering services provided by wetlands in arid and semi-arid regions and provides a knowledge base that can …

Microbial Impacts On Endocrine Disrupting Contaminants: Las Vegas Wash And Lake Mead, Nevada, Susanna May Blunt

UNLV Theses, Dissertations, Professional Papers, and Capstones

International concern over endocrine disrupting chemicals (EDCs) has become heightened in recent years as more studies reveal their persistence in the environment and their detrimental effects on wildlife. However, little is known about the role of microorganisms in the fate and transport of these compounds in surface waters. Las Vegas Wash, a stream flowing into Lake Mead and fed primarily by treated wastewater effluent, provided a unique experimental system in which to study the role microorganisms play in the dispersal of these compounds in aquatic systems. Samples were collected from the Las Vegas Wash downstream of the Las Vegas Valley's …

Bryoecology In The American Southwest: Patterns Of Biodiversity And Responses To Global Change, John Carroll Brinda

UNLV Theses, Dissertations, Professional Papers, and Capstones

This dissertation combines investigation of the large-scale responses of bryophyte species diversity and distribution with small-scale physiological adaptations to global change. These two areas of inquiry are linked because one way to predict plant species responses to global change is to examine their distribution across current ecological gradients produced by factors such as latitude and elevation. By examining these biogeographic patterns one can identify those species that have a narrow tolerance and therefore are most sensitive to change. Selected bryophytes might then be used as indicator species in long-term monitoring programs. Where historical data exist, these can be used to …

Co-Development Of Biological Soil Crusts, Soil-Geomorphology, And Landscape Biogeochemistry In The Mojave Desert, Nevada, U.S.A. – Implications For Ecological Management, Amanda Jean Williams

UNLV Theses, Dissertations, Professional Papers, and Capstones

Biological soil crusts (BSCs) are complex matrices of soil particles, mosses, lichens, and cyanobacteria that prevent erosion and influence water and energy balances, soil fertility, and vascular plant germination. The processes that form BSCs, the factors that control their distribution, and the ecosystem feedbacks that they sustain are poorly understood. This dissertation employed a novel interdisciplinary approach to address those research unknowns through investigations of the micromorphological structure, soil-geomorphic relationships, and biogeochemical feedbacks of BSCs in the Mojave Desert.

A micromorphological study of BSCs resulted in a succession model that illustrates how crust formative processes and structures change through time. …

Reconstructing Species Responses To Past Climatic Changes Using Niche Modeling And Genetic Data, Tereza Jezkova

UNLV Theses, Dissertations, Professional Papers, and Capstones

Glacial – interglacial cycles have a pronounced impact on species distributions and genetic structure. Many species shift their distributions to lower latitudes and altitudes during the colder glacial periods and expand northwards and up the elevation during warmer interglacial periods. Some species however are capable of adapting to changing environment which allows them to persist in place despite climatic changes. I explored how climatic changes after the last glacial maximum (LGM) effected two species inhabiting the deserts of western North America: one mammal (Chisel-toothed Kangaroo Rat, Dipodomys microps) and one reptile (Desert Horned Lizard, Phrynosoma platyrhinos). I used …

Filtration And Growth Rate Of Lake Mead Quagga Mussels (Dreissena Bugensis) In Laboratory Studies And Analyses Of Bioaccumulation, Carolyn Louise Link

UNLV Theses, Dissertations, Professional Papers, and Capstones

In January of 2007, Quagga Mussels (Dreissena bugensis) were identified in Lake Mead, Nevada. An aquatic invasive species, these mussels can significantly alter ecosystems. This study sought to quantify three ecological traits of the species through a series of laboratory experiments and analyses, providing information both for comparison with Dreissena in other locations, as well as for limnologic management decisions. Filtration rate of quagga mussels was quantified using algal strains and natural seston. Two strains of green algae, Nannochloris and Scenedesmus were used to determine mussel filtration rates with a spectrophotometer. Quagga filtration rates of collected Lake Mead seston were …

Distribution And Site Selection Of Le Conte's And Crissal Thrashers In The Mojave Desert: A Multi-Model Approach, Dawn Marie Fletcher

UNLV Theses, Dissertations, Professional Papers, and Capstones

Information on the distribution and habitat requirements of a species are critical components to the development of meaningful conservation plans. Such knowledge, however, is particularly difficult to obtain for species that are elusive and occur at low densities, such as the Le Conte's ( Toxostoma lecontei ) and Crissal (Toxostoma crissale ) thrashers. In association with a regional conservation plan, I evaluated the distribution and habitat selection of these thrashers within Clark County, Nevada in the eastern Mojave Desert. I used a call-broadcast approach to sample 432 stratified random locations, detecting Le Conte's thrashers at 45 locations and Crissal …

Water Quality Changes In A Constructed Wetland At The Springs Preserve In Las Vegas, Nevada, Aaron Mathis Miller

UNLV Theses, Dissertations, Professional Papers, and Capstones

The Springs Preserve near downtown Las Vegas, Nevada contains a seven-acre constructed wetland. Springs Preserve managers are planning to use water from the constructed wetland to irrigate creeks immediately north of the wetland. These creeks will be used by a variety ofaquatic wildlife, including endangered amphibians sensitive to harmful metalloids, such as selenium, lead, and arsenic.

In an attempt to answer toxicological questions about contaminant concentrations in the constructed wetland, three metals and metalloids (selenium, arsenic, and lead), two nutrients (nitrogen and phosphorus), and the major ionic species were analyzed at four sampling locations for aqueous concentrations, in two separate …

A Comparison Of Population Sizes And Number Of Captures For The Desert Woodrat (Neotoma Lepida) In Two Microhabitats In The Las Vegas Wash, Nevada, Jayson Barangan

UNLV Theses, Dissertations, Professional Papers, and Capstones

Planned removal and eradication of saltcedar in the Las Vegas Wash, Nevada could potentially generate adverse impacts on present desert woodrat (Neotoma lepida) populations inhabiting the area. Consequently, research was conducted investigating population sizes of N. lepida in two distinct microhabitat types, saltcedar (Tamarix sp.) and mesquite/quailbush (Prosopis sp./Atriplex lentiformis). The results of this study will aid in gauging the effects of the changes in vegetation once restoration work is completed and assist with logistical scheduling for implementation of control measures. Mark-recapture field techniques were utilized for data collection from July 2002 to June 2003. Population estimates were calculated using …

The Effects Of Off-Road Vehicle Use In Desert Tortoise (Gopherus Agassizii) Habitats, Brent D. Clark

UNLV Theses, Dissertations, Professional Papers, and Capstones

The desert tortoise (Gopherus agassizii) populations have been in decline and have been placed on the endangered species list. No single factor is ultimately responsible for the tortoise decline. It is a combination of events that collectively have a negative impact. I chose to focus my study on only one factor, off-road vehicles. By evaluating the damage done to the terrain by off-road vehicles, a better understanding of their impact on the tortoise populations can be assessed and protective measures taken.

The amount of available vegetation does not seem to play a role in their decisions of which plants to …

An Ethical Framework For Interpreting The United States Endangered Species Act, Cathryn M. Elgin

UNLV Theses, Dissertations, Professional Papers, and Capstones

In this study I argue that a holistic approach is better than an individualistic approach for interpreting the United States Endangered Species Act (ESA). I propose that the use of a holistic ethical framework, based on fundamental environmental philosophy, is better in that it more effectively fulfills the ESA's goals of species and ecosystem conservation. Holistic ethics is based on concern for a community as a whole, while individualistic ethics is based on concern for the individual. A holistic approach, I argue, is more beneficial to nature than is an individualistic approach or other non-holistic approaches. I set up basic …