Geoarchaeology -- Pre-Clovis archaeology -- Site search strategies.

Temperature plays a crucial role in the constant interaction between organisms and the environment. It affects development and rates of physiological functions as well as survival of organisms.

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abstract: Echinomastus erectocentrus (J.M. Coulter) Britton & Rose var. acunensis (W.T. Marshall) Bravo, the Acuña cactus, is a small, single-stemmed spherical cactus with a restricted distribution across the Sonoran Desert in southern Arizona and into northern Sonora, Mexico. Populations of E. erectocentrus var. acunensis are threatened by loss of habitat, climate change, predation, and border related impacts. Due to the severity of these threats and shrinking population sizes, E. erectocentrus var. acunensis was federally listed as endangered by the United States Fish and Wildlife Service in 2013. The varieties of Echinomastus erectocentrus, E. erectocentrus var. acunensis and E. erectocentrus var. erectocentrus (J.M. Coulter) Britton & Rose, share many morphological characteristics that make them difficult to distinguish from one another. Echinomastus johnsonii (Parry ex Engelm.) E.M. Baxter, a presumed closely related species, also has a high level of morphological overlap that further complicates our understanding of species boundaries and detailed morphological data for these three taxa indicate a geographical cline. The goal of this project is to document the genetic diversity within and among populations of E. erectocentrus var. acunensis, and its close relatives E. erectocentrus var. erectocentrus and E. johnsonii. To accomplish this, populations of E. erectocentrus var. acunensis, E. erectocentrus var. erectocentrus, E. johnsonii and the outgroup Echinomastus intertextus (Engelm.) Britton & Rose were sampled. Deoxyribonucleic acid (DNA) was extracted, and data were collected for nine microsatellite regions developed specifically for these taxa, and two microsatellite regions developed for Sclerocactus, a closely related genus. Standard population genetic measures were used to determine genetic variation and structure, and this observed genetic differentiation was then compared to the current morphological understanding of the group. These analyses help improve the knowledge of the genetic structure of E. erectocentrus var. acunensis and inform the understanding of species boundaries and evolutionary relationships within the group by revealing genetic distinctiveness between all four taxa and hybrid populations between the two varieties. This information also reveals patterns of gene flow and population locations that have the highest conservation priority, which can be incorporated into efforts to conserve and protect this endangered species. / Dissertation/Thesis / Masters Thesis Plant Biology and Conservation 2020

abstract: Ecotourism is defined as a traveling distance where tourist interact with environment and enjoy nature. It is a market segment in the tourism sector that can provide several benefits if managed properly. Although ecotourism can provide economic benefits for Saudi Arabia, there is not enough attention granted to ecotourism facilities and services in desert sites. The current study attempts to fill this gap by aiming to explore families’ perceptions of environmental desert settings that support their ecotourism needs and to identify opportunities to develop services, expand activities areas, and infrastructures. Ultimately, this study addresses families’ ecotourism needs for the promotion of sustainable desert ecotourism development that is inclusive to most Saudi tourists. This study uses qualitative research methods, including observations, surveys and interviews of families who have visited Saudi Arabian deserts between December 2019 and March 2020. The findings are analyzed and translated into a set of design guidelines for existing and for new sustainable ecotourist sites within Saudi Arabian desert environments. The implications of this study are two-fold: to (1) educate the design industry to take into account ecotourism visitors’ perceptions of environmental settings and infrastructures needs without compromising its natural resources; and (2) highlight the value of sustainable ecotourism so that decision makers take an action to ensure stability of the growing market demand of desert tourism. This study concludes with a discussion of findings reached that can promote more sustainable ecotourism experiences at Saudi Arabian desert sites. / Dissertation/Thesis / Masters Thesis Design 2020

abstract: Desert ecosystems of the southwest United States are characterized by hot and arid climates, but hibernating bats can be found at high altitudes. The emerging fungal infection, white-nose syndrome, causes mortality in hibernating bat populations across eastern North America and the pathogen is increasingly observed in western regions. However, little is known about the ecology of hibernating bats in the southwest, which can help predict how these populations may respond to the fungus. My study investigated hibernating bats during two winters (2018-2019/2019-2020) at three caves in northern Arizona to: (1) describe diversity and abundance of hibernating bats using visual internal surveys and photographic documentation, (2) determine the duration of hibernation by recording bat echolocation call sequences outside caves and recording bat activity in caves using visual inspection, and (3) describe environmental conditions where hibernating bats are roosting. Adjacent to bats, I collected temperature and relative humidity, which I converted into absolute humidity. I documented hibernation status (i.e. active vs. not active) and roosting body position (i.e. open, partially hidden, and hidden). Between September 2018 and April 2019, 246 bat observations were recorded across the three caves. The majority of bats were identified as Myotis spp. (45.9\%, n=113), followed by Corynorhinus townsendii (45.5\%, n=112), Parastrellus hesperus (4.8\%, n=12), Eptesicus fuscus (3.6\%, n=9). Between September 2019 and April 2020, I documented a total of 361 bat observations across the three caves. C. townsendii was most prevalent (52.9\%, n=191), followed by the category P. hesperus/Myotis spp. (25.7\%, n=93), Myotis spp. (12.4\%, n=45), P. Hesperus (4.4\%, n=16), E. fuscus (3.6\%, n=13) and Unknown (0.8\%, n=3). Average conditions adjacent to bats were, temperature=12.5ºC, relative humidity=53\%, and absolute humidity=4.9 g/kg. Hibernating bats were never observed in large clusters and the maximum hibernating population size was 24, suggesting low risk for pathogen transmission among bats. Hibernation lasted approximately 120 days, with minimal activity documented inside and outside caves. Hibernating bats in northern Arizona may be at low risk for white-nose syndrome based on population size, hibernation length, roosting behavior, and absolute humidity, but other variables (e.g. temperature) indicate the potential for white-nose syndrome impacts on these populations. / Dissertation/Thesis / Masters Thesis Biology 2020

Here, we embarked a bioprospecting project that focuses on the isolation and characterization of plant root endophytes, collected from the Thar Desert. A total of 381 endophytes were isolated and based on their 16S rRNA gene sequences, genus Bacillus (58 strains) was identified as the major taxon and only endophytes from this genus were isolated from all plant types. Of the 58 Bacillus strains, only 16 strains were selected for screening of plant growth promotion traits such as P and Zn solubilization, indole-3-acetic acid and siderophore production, and antimicrobial activity. Based on the presence of specific plant growth promotion traits 10 strains were shortlisted for further in vitro screening with A. thaliana; to confirm that these bacteria can confer resilience to plants under salt stress conditions. B. circulans (PK3-15 and PK3-109), B. cereus (PK6-15) B. subtilis (PK3-9) and B. licheniformis (PK5-26) displayed the ability to increased the fresh weight of A. thaliana under salt stress conditions by more than 50 % compared to the uninoculated control. An interesting observation was that B. circulans (PK3-109) (shown to produce IAA exopolysaccharide) and B. circulans (PK3-138) (shown to produce IAA) in vitro results were substantially different as B. circulans (PK3-138) decreased the total fresh weight of A. thaliana by 47 %, whilst B. circulans (PK3-109) was one of the best performing strains. Thus, the genomes of these two strains were sequences to unravel the molecular versatility of B. circulans strains, specifically with respect to their interaction with plants. Most of the genome of these strains is identical but the most interesting feature was the presence of 1/ the DegS–DegU two-component system that is known to mediate the salt stress response and DegU also represses toxin wapA similar to antitoxin wapI, and 2/ YxiG, a gene in the unique orthogroup of PK3-109 was found to be linked to WapI. Thus, PK3-138 substantially decreasing the total fresh weight of A. thaliana under salt stress conditions suggests that the toxic activity of a toxin such as WapA is not effectively ameliorated by the antitoxin such as WapI in the absence of a functional YxiG gene.

One of the major challenges for agricultural research in the 21st century is to increase crop productivity to meet the growing demand for food and feed. Biotic (e.g. plant pathogens) and abiotic stresses (e.g. soil salinity) have detrimental effects on agricultural productivity, with yield losses being as high as 60% for major crops such as barley, corn, potatoes, sorghum, soybean and wheat, especially in semi-arid regions such as Saudi Arabia. Plant growth promoting bacteria isolated from pioneer desert plants could serve as an eco-friendly, sustainable solution for improving plant growth, stress tolerance and health. In this dissertation, culture-independent amplicon sequencing of bacterial communities revealed how native desert plants influence their surrounding bacterial communities in a phylogeny-dependent manner. By culture-dependent isolation of the plant endosphere compartments and a number of bioassays, more than a hundred bacterial isolates with various biochemical properties, such as nutrient acquisition, hormone production and growth under stress conditions were obtained. From this collection, five phylogenetically diverse bacterial strains were able to promote the growth of the model plant Arabidopsis thaliana under salinity stress conditions in a common mechanism of inducing transcriptional changes of tissue-specific ion transporters and lowering Na+/K+ ratios in the shoots. By combining a number of in vitro bioassays, plant phenotyping and volatile-mediated inhibition assays with next-generation sequencing technology, gas chromatography–mass spectrometry and bioinformatics tools, a candidate strain was presented as a multi-stress tolerance promoting bacterium with potential use in agriculture. Since recent research showed the importance of microbial partners for enhancing the growth and health of plants, a review of the different factors influencing plant-associated microbial communities is presented and a framework for the successful application of microbial inoculants in agriculture is proposed. The presented work demonstrates a holistic approach for tackling agricultural challenges using microbial inoculants from desert plants by combining culturomics, phenomics, genomics and transcriptomics. Microbial inoculants are promising tools for studying abiotic stress tolerance mechanisms in plants, and they provide an eco-friendly solution for increasing crop yield in arid and semi-arid regions, especially in light of a dramatically growing human population and detrimental effects of global warming and climate change.

Under the extreme arid conditions of deserts, long periods of drought, nutrient-poor soils and high temperatures severely challenge the primary productivity of the ecosystem. Desert plants have evolved morphological and physiological adaptations against abiotic stresses. Along with these adaptation strategies they can recondition their surrounding soil, which will result in the enrichment of nutrients and moisture in the soil surrounding the plant. Although such self-fertilization may support the growth of other sympatric plant species under the plant, competitive exclusion mechanisms (i.e., allelopathy) reduce this possibility. Consequently, this will affect the diversity and functionality of the edaphic microbial communities. I hypothesize that desert xerophytes recondition the soils surrounding their body along with combining the ‘fertility’ and ‘allelopathy’ mechanisms to create a favorable new niche in desert ecosystem. I tested this hypothesis on the soil reconditioned by Welwitschia mirabilis growing in its native environment, the Namib Desert, Namibia. The collected soils were first used to confirm that Welwitschia manipulates the surrounding soil creating a ‘fertile’ but ‘exclusive’ soil area around the plant. Along with evaluating the effect of the reconditioned soil on the germination and plant development under normal irrigation and controlled drought condition, using barley as phytometer. The physio-chemical (i.e., WHC and WP) and microbial community analyses demonstrate that W. mirabilis reconditions the surrounding soil creating an environmental gradient around itself, in which the fertility is increased, through the accumulation and incorporation of shed reproductive parts of the plants (i.e., cones) in the surrounding soil, that will stimulate the plant growth under drought stress. Along with the fertilization effect, soil reconditioning also favor the antagonist effect (i.e., allelopathy) against plant competitors (e.g., new germinating seeds) to protect its ecological niche. Furthermore, the microorganisms and/or soluble/thermolabile molecules contribute to the allelopathic effect activated by the soil-reconditioning around W. mirabilis. The interactions among W. mirabilis, soil and microbes highlight an adaptive strategy that combines soil fertilization and allelopathy that I defined as “Alleolofertility” strategy. This allelofertility island surrounding the W. mirabilis may contributes to explain the evolutionary success of such a ‘living fossil’.

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