Desert Ecology Commons^™

Examining The Relationship Between Climate And Seasonal Stream Thermal Regimes In A High Desert Ecosystem, Hannah Moore, Melody Feden

Scholars Week

Climate change is negatively affecting ecosystems around the world, and in the coming years, scientists predict that these changes will only intensify and accelerate. In the western mountains of North America, climate change projections predict elevated temperatures, reduced snowpack, and earlier snowmelt. Elevated air temperatures have the propensity to affect water temperatures in sensitive freshwater ecosystems. Temperature increases may cause streams to reach the upper thermal limit for many aquatic organisms, such as aquatic invertebrates and fish, and result in death or dispersal for these organisms. This makes the availability of cold-water refugia in streams that much more important for …

Can Omnivores Mediate The Effects Of Degradation?, Hannah Moore

Scholars Week

Omnivores feed at multiple trophic levels and have large effects on community structuring and stability. The magnitude and direction of such effects, whether omnivores stabilize or destabilize communities, remains unresolved. Shifts in omnivore diet and trophic position may be of particular importance to community stability in degraded habitats, where resources are sparse. For example, omnivores may reduce the severity and duration of community responses to degradationby dampening the effects of any disturbance-mediated trophic cascade. The relatively simple food webs of freshwater systems are ideal for studying trophic ecology, and in the western U.S., streams are heavily degraded by overgrazing, beaver …

Environmental Effects On Drosophila Brain Development And Learning, Xia Wang, Amei Amei, J. Steven De Belle, Stephen P. Roberts

Biological Sciences Faculty Research & Creative Works

Brain development and behavior are sensitive to a variety of environmental influences including social interactions and physicochemical stressors. Sensory input in situ is a mosaic of both enrichment and stress, yet little is known about how multiple environmental factors interact to affect brain anatomical structures, circuits and cognitive function. In this study, we addressed these issues by testing the individual and combined effects of sub-adult thermal stress, larval density and early-adult living spatial enrichment on brain anatomy and olfactory associative learning in adult Drosophila melanogaster. In response to heat stress, the mushroom bodies (MBs) were the most volumetrically impaired among …

The North American Quails, Partridges, And Pheasants, Paul A. Johnsgard

Zea E-Books Collection

This book documents the biology of six species of New World quails that are native to North America north of Mexico (mountain, scaled, Gambel’s, California, and Montezuma quails, and the northern bobwhite), three introduced Old World partridges (chukar, Himalayan snowcock, and gray partridge), and the introduced common (ring-necked) pheasant. Collectively, quails, partridges, and pheasants range throughout all of the continental United States and the Canadian provinces. Two of the species, the northern bobwhite and ring-necked pheasant, are the most economically important of all North American upland game birds. All of the species are hunted extensively for sport and are highly …

The Impact Of Climate And Elevation On The Growth And Mortality Of Piñon Pine, Alice M. Fretz

Biology ETDs

The Southwestern United States is currently experiencing severe drought, resulting in the mortality of many tree species. Piñon-juniper woodlands are an extensive biome in the Southwest, and are highly vulnerable to extended periods of drought that lead to tree mortality. Specifically, Pinus edulis populations are decreasing due to increasingly arid conditions. I used dendrochronology to investigate how tree growth rings of Pinus edulis reflect severe drought in living and dead trees. I also investigated how severe drought affects Pinus edulis along an altitudinal gradient. Tree core samples were taken from currently living and dead trees, as well as from trees …

Divergence In Life History Traits Between Two Populations Of A Seed-Dimorphic Halophyte In Response To Soil Salinity, Fan Yang, Jerry M. Baskin, Carol C. Baskin, Xuejun Yang, Dechang Cao, Zhenying Huang

Biology Faculty Publications

Production of heteromorphic seeds is common in halophytes growing in arid environments with strong spatial and temporal heterogeneity. However, evidence for geographic variation (reflecting local adaptation) is almost nonexistent. Our primary aims were to compare the life history traits of two desert populations of this halophytic summer annual Suaeda corniculata subsp. mongolica and to investigate the phenotypic response of its plant and heteromorphic seeds to different levels of salt stress. Dimorphic seeds (F₁) of the halophyte S. corniculata collected from two distant populations (F₀) that differ in soil salinity were grown in a common environment under …

Precipitation Patterns And Fungal Community Succession In A Seasonally Dry Secondary Tropical Savanna, Sara R. López-Rodríguez

Biology ETDs

In the northwestern part of South America, seasonally dry forests have undergone extensive conversion to savannas to support ranching and agriculture. The combination of fire and vegetation removal employed for clearing, together with extensive agricultural practices, often lead to loss of soil fertility. This results in land that is no longer useful for agriculture and on which historical forests are unable to regenerate. This study examined the effects of common agricultural practices on soil fungal communities by simulating the effects of fire followed by plant removal. The goal was to determine whether common practices have rapid effects on soil communities, …

Plant-Microbial Interactions Are Strong Determinants Of Plant Population And Community Dynamics, Yan-Yi Anny Chung 9485698

Biology ETDs

Plant-microbial interactions are ubiquitous and yet the consequences of these interactions on plant population and community dynamics are relatively unknown. Here, we used two different classes of plant-microbial interactions to examine their effects on key plant population and community characteristics such as commonness and rarity, competition and coexistence, as well as community stability.

Vertically-transmitted endophytes had stage-dependent effects on the population growth of two grass species Poa sylvestris and Poa alsodes, and generally increased host population growth rates. However, it was the intrinsic demographic advantage of P. sylvestris that allowed its population to grow at a much faster rate …

Effects Of Wildfires On Rattlesnake (Crotalus Oreganus) Growth And Movement In Washington State, Joseph Chase

All Master's Theses

Fire is a dominant force in the Pacific Northwest that shapes ecosystems and influences wildlife, yet little is known of its effects on local predators. Northern Pacific rattlesnakes (Crotalus oreganus) comprise an excellent model to investigate how fire may influence wildlife because they are important predators that contribute to controlling prey populations, but are also unable to readily escape from wildfires. We developed a novel technique to assess growth rates of rattlesnakes by using digital photography to analyze differences in widths of their rattle segments laid down over time. We compared growth rates of rattlesnakes in habitats that …

Phytophagous Insect Oviposition Shifts In Response To Probability Of Flower Abortion Owing To The Presence Of Basal Fruits, Shivani Jadeja, Brigitte Tenhumberg

School of Biological Sciences: Faculty Publications

Phytophagous insects use a wide range of indicators or associated cues to avoid laying eggs in sites where offspring survival is low. For insects that lay eggs in flowers, these unsuitable sites may be created by the host plant’s resource allocation to flowers. In the sequentially flowering host plant, Yucca glauca, late-opening distal flowers are more likely to be aborted in the presence of already-initiated basal fruits because they are strong resource sinks. If flowers are aborted, all eggs of the phytophagous insect, Tegeticula yuccasella, within the flower die. We used the phytophagous insect T. yuccasella that lays …

Plant-Biocrust Interactions Mediated By The Fungal Loop, Eva Dettweiler-Robinson

Biology ETDs

Plant-microbial interactions influence biogeochemical cycles. Plants and biological soil crusts are primary producers in drylands. Biocrusts include cyanobacteria, lichens, mosses, algae, fungi, bacteria, and archaea on the soil surface, some of which fix atmospheric nitrogen. I investigated controls on biocrust carbon fluxes and their contribution to ecosystem fluxes, the incorporation of plant-derived carbon into biocrusts, and the role of soil fungi in promoting performance of plants and biocrusts. Biocrusts responded to temperature and moisture differently by biome. Biocrusts in grasslands/shrublands contributed >25% of total summertime ecosystem respiration, but biocrusts in savannas/woodlands contributed < 1%. Biocrusts contributed < 2% to GPP in any biome. To augment their native photosynthesis, biocrusts may include 16% plant-derived carbon. Fungal connections improved plant and biocrust performance and reduced differences in the CN ratio between organisms compared to when connections were impeded. Investigation of interactions among biocrusts, plants, and fungi has improved understanding of resource cycling in drylands.

Comparative Population Genomics And Speciation Of Snakes Across The North American Deserts, Edward A. Myers

Dissertations, Theses, and Capstone Projects

Understanding the process of speciation is of central interest to evolutionary biologists. Speciation can be studied using a phylogeographic approach, by identifying regions that promote lineage divergence, addressing whether speciation has occurred with gene flow, and when extended to multiple taxa, addressing if the same patterns of speciation are shared across codistributed groups with different ecologies. Here I examine the comparative phylogeographic histories and population genomics of thirteen snake taxa that are widely distributed and co-occur across the arid southwest of North America. I first quantify the degree to which these species groups have a shared history of population divergence …

The Effects Of Drought On Diets Of Apex Predators In The South African Lowveld Inferred By Fecal Hair Analysis, Shelby Wade

Mahurin Honors College Capstone Experience/Thesis Projects

To properly manage offtake quotas and conservation efforts, Balule Nature Reserve (South Africa) instituted a study in 2014 to determine prey species selection by megapredators. In 2015, Balule Nature Reserve received about 190 mm less rainfall between the months of January and June than in 2014 (116 mm less than average). This study compares the diets of lions and hyaenas between 2014 and 2015. Prey species consumed were determined by fecal analysis, and results were compared to prey availability. Sixteen, 1 km2 plots were chosen from the 400 km2 Reserve. Between June and August 2015, we walked three, 1 km …

Consequences Of Pre-Inoculation With Native Arbuscular Mycorrhizae On Root Colonization And Survival Of Wyoming Big Sagebrush (Artemisia Tridentata Ssp. Wyomingensis) Seedlings After Transplanting, Bill Eugene Davidson

Boise State University Theses and Dissertations

Inoculation of seedlings with arbuscular mycorrhizal fungi (AMF) is a common practice aimed at improving seedling establishment. The success of this practice largely depends on the ability of the inoculum to multiply and colonize the growing root system after transplanting. These events were investigated in Artemisia tridentata ssp. wyomingensis (Wyoming big sagebrush) seedlings inoculated with native AMF. Seedlings were first grown in a greenhouse in sterilized soil (non-inoculated seedlings) or soil containing a mixture of native mycorrhizae (inoculated seedlings). Three-month old seedlings were transplanted to 24 L pots containing soil from a sagebrush habitat (mesocosm experiments) or to a recently …

Plant-Soil Relations On Gypsum And Non-Gypsum Soils Of The Chihuahuan Desert, Clare Muller

Senior Honors Projects

No abstract provided.

Speed And Resolution In The Age Of Technological Reproducibility, Shawn Taylor

Theses and Dissertations

The rate of acceleration of the biologic and synthetic world has for a while now, been in the process of exponentially speeding up, maxing out servers and landfills, merging with each other, destroying each other. The last prehistoric relics on Earth are absorbing the same oxygen, carbon dioxide and electronic waves in our biosphere as us. A degraded .jpeg enlarged to full screen on a Samsung 4K UHD HU8550 Series Smart TV - 85” Class (84.5” diag.). Within this composite ecology, the ancient limestone of the grand canyon competes with the iMax movie of itself, the production of Mac pros, …

Photosynthetic Thermal Tolerance And Recovery To Short Duration Temperature Stress In Desert And Montane Plants: A Comparative Study, David William Gallagher

Master's Theses

• Climate change models predict an increase in frequency and amplitude of extreme weather events, including heat waves. To better predict how the composition and distribution of plant assemblages might respond to these changes in temperature, it is important to understand how species currently respond to these extremes. Photosynthetic thermal tolerance (T₂₅)and photosynthetic recovery (RT₂₅) were quantified in 27 species. We also studied the relationships between T₂₅, RT₂₅ and leaf mass per area (LMA). Leaf temperature was also monitored in the field.
• Leaves used in this study were collected from two distinct …

Assessing Growth Response To Climate Controls In A Great Basin Artemisia Tridentata Plant Community, Lorenzo F. Apodaca

UNLV Theses, Dissertations, Professional Papers, and Capstones

An assessment of the growth response of key vegetative species to climatic variability is vital to identifying possible local impacts on ecosystems faced with imminent climate change. With current climate projections in Nevada predicting a shift to an even more arid climate with greater year-to-year variability, the imperative exists to identify the effects of specific climatic controls on plant growth and to research methods to assess large-scale vegetative changes, especially in more remote areas where readily available data sets may be lacking. This study utilized annual growth ring indices constructed from big sagebrush (Artemisia tridentatassp.tridentata) stems collected in Spring Valley, …

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 …

Restoration Of Biological Soil Crust On Disturbed Gypsiferous Soils In Lake Mead National Recreation Area, Eastern Mojave Desert, Lindsay P. Chiquoine

UNLV Theses, Dissertations, Professional Papers, and Capstones

Biological soil crusts (BSCs) are sensitive to anthropogenic disturbances. Natural recovery takes many years. Active restoration decreases recovery time. Native BSC inocula, which included lichens and mosses, salvaged from gypsiferous soil habitats in Lake Mead National Recreation Area (LMNRA) in the eastern Mojave Desert were stored dry for two years and applied to disturbed soil after a road reconstruction in LMNRA and also used in laboratory experiments to test inoculation technique effectiveness. After 18 months, field results revealed positive relationships between inoculation and the presence of macroscopic BSC cover, cyanobacteria abundance, soil stability, and ammonium concentrations. Chlorophyll fluorescence monitoring of …

Soil Nematodes And Their Prokaryotic Prey Along An Elevation Gradient In The Mojave Desert (Death Valley National Park, California, Usa), Amy M. Treonis, Kelsey Sutton, Brendan Kavanaugh, Archana Narla, Timothy Mcllarky, Jasmine Felder, Cecilia O'Leary, Megan Riley, Alyxandr Pikus, Sarah Thomas

Biology Faculty Publications

We characterized soil communities in the Mojave Desert across an elevation gradient. Our goal was to test the hypothesis that as soil quality improved with increasing elevation (due to increased productivity), the diversity of soil prokaryotes and nematodes would also increase. Soil organic matter and soil moisture content increased with elevation as predicted. Soil salinity did not correlate to elevation, but was highest at a mid-gradient, alluvial site. Soil nematode density, community trophic structure, and diversity did not show patterns related to elevation. Similar results were obtained for diversity of bacteria and archaea. Relationships between soil properties, nematode communities, and …

Scorpion Phylogeography In The North American Aridlands, Matthew Ryan Graham

UNLV Theses, Dissertations, Professional Papers, and Capstones

Understanding the geographic, geologic, and climatic forces responsible for generating current patterns of biodiversity has been a central objective of phylogeography. To develop a better understanding of these processes in the North American arid lands, I used DNA sequence data and species distribution modeling to conduct three phylogeographic assessments incorporating four species of arid-adapted scorpions:Hadrurus arizonensis, H. jedediah, H. spadix,and Paruroctonus becki. In an assessment of H. arizonensis, phylogeographic patterns indicate that Pleistocene climate cycles and associated glacial refugia played a central role in structuring the genetic diversity of this species in the Mojave and Sonoran deserts, mostly supporting predictions …

Mojave Applied Ecology Notes Fall 2011, E. Cayenne Engel, Scott R. Abella, Kathryn A. Prengaman, Jason Whited, Peter Michel

Mojave Applied Ecology Notes

Paper on impacts of Mojave wildfires through time published, possibilities of catastrophic Mt. Charleston forest fires, vegetation mapping at three national parks, UNLV library’s special collections, and the benefits of scientific publications to managers and stakeholders

Mojave Applied Ecology Notes Summer 2011, Scott R. Abella, Charles W. Denton, David G. Brewer, Rory W. Steinke, Wayne A. Robbie, W. Wallace Covington, E. Cayenne Engel, Ross Guida

Mojave Applied Ecology Notes

Thoughts on fire possibilities on Mount Charleston, estimating historical densities of Ponderosa pine in northern AZ, over-understory changes in the Spring Mountains, seeding effectiveness in Red Rock Canyon, workshop announcements.

Phylogeography Of Three Heteromyid Taxa: Insight On The Evolution Of A North American Arid Grassland Rodent Guild, Sean A. Neiswenter

UNLV Theses, Dissertations, Professional Papers, and Capstones

Revealing how communities are shaped by abiotic and biotic factors plays a central role in biogeographic and comparative phylogeographic studies. The biogeography of North American arid grasslands is explored using nuclear and mitochondrial DNA from three groups of heteromyid rodents that are broadly sympatric in aridlands across western North America. Phylogenetic and molecular clock analyses are used to estimate the timing of divergences within each group. A general pattern of late Miocene divergence and expansion of lineages in each of the groups that is coincident with the rapid expansion of arid grasslands at the time. The initial divergence is followed …

Mojave Applied Ecology Notes Spring 2011, Scott R. Abella, Ross Guida, S. D. Smith, Christopher L. Roberts, Haroon Stephen, William J. Smith, Zhongwei Liu, James S. Holland, Aurore Giguet

Mojave Applied Ecology Notes

Red brome distribution in the eastern Mojave Desert, A look at the UNLV xeric gardens and Marjorie Barrick museum, Summary of recent science synthesis efforts

Mojave Applied Ecology Notes Winter 2011, Scott R. Abella, Alice C. Newton, Kenneth Chittick, Pam Sinanian

Mojave Applied Ecology Notes

Lake Mead’s collaborative applied science research program; “annoying the elephant” - ruminations on active management by Alice Newton, Lake Mead NRA vegetation manager; 2012 NWRA Lake Mead symposium sneak peak; assessing forest change using dendrochronology in the Spring Mountains.

Mojave Applied Ecology Notes Fall 2010, Adria Decorte, Sharon Altman, Alex Suazo

Mojave Applied Ecology Notes

Adria DeCorte defense, Mojave desert inventory and monitoring mapping project, effect of burial depth on Brassica tournefortii seeds

Mojave Applied Ecology Notes Summer 2010, Scott R. Abella, E. Cayenne Engel

Mojave Applied Ecology Notes

Survey of monitoring and management for conservation of rare plants, Roadside restoration techniques in Joshua Tree NP, and an update on renewable energy developments in the Southwestern deserts

Phylogeography Of Two Closely Related Anurans, The Relict Leopard Frog (Rana Onca) And Lowland Leopard Frog (Rana Yavapaiensis), Viktoria Hemmings

UNLV Theses, Dissertations, Professional Papers, and Capstones

I investigate the phylogeography of the relict and lowland leopard frogs (Rana onca; R. yavapaiensis) inhabiting the Mojave and Sonoran deserts. In Chapter 1, I summarize literature describing taxonomy, phylogenetics, and the possible effects of Quaternary climate change on distribution. Examples of phylogeographic patterns from generally co-distributed organisms are provided to develop background for interpreting the structure. In Chapter 2, I investigate the phylogeography of these frogs using mitochondrial DNA data. The analysis supports a previously determined phylogenetic break between taxa however further dividing R. yavapaiensis into two lineages. I estimate a possible Early Pleistocene divergence of R. onca and …