Understanding how climatic variation affects animal populations and communities is essential for addressing threats posed by climate change, especially in systems where impacts are projected to be high. We evaluated abundance dynamics of five common species of diurnal lizards over 25 years in a Sonoran Desert transition zone where precipitation decreased and temperature increased across time, and assessed hypotheses for the influence of climatic flux on spatiotemporal variation in abundances. We repeatedly surveyed lizards in spring and summer of each year at up to 32 sites, and used hierarchical mixture models to estimate detection probabilities, abundances, and population growth rates. Among terrestrial species, abundances of a short-lived, winter-spring breeder increased markedly by an estimated 2375285% across time, while two larger spring-summer breeders with higher thermal preferences declined by up to 64%. Abundances of two arboreal species that occupy shaded and thus sheltered microhabitats fluctuated but did not decline systematically. Abundances of all species increased with precipitation at short lag times (151.5 yrs) likely due to enhanced food availability, but often declined after periods of high precipitation at longer lag times (254 yrs) likely due to predation and other biotic pressures. Although rising maximum daily temperatures (Tmax) are expected to drive global declines of lizards, associations with Tmax were variable and weak for most species. Instead, abundances of all species declined with rising daily minimum temperatures, suggesting degradation of cool refugia imposed widespread metabolic or other costs. Our results suggest climate warming and drying are having major impacts on lizard communities by driving declines of species with traits that augment exposure to abiotic extremes and by modifying species interactions. The complexity of patterns we report indicate that evaluating and responding to the influence of climate change on biodiversity must consider a broad array of ecological processes.

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: There is an ongoing debate around the extent that anthropogenic processes influence both plant species distribution dynamics and plant biodiversity patterns. Past human food use may leave a strong legacy on not only the extent that food plants are dispersed and fill their potential geographic ranges, but also on food plant species richness in areas that have been densely populated by humans through time. The persistent legacy of plant domestication on contemporary species composition has been suggested to be significant in some regions. However, little is known about the effects that past human food use has had on the biogeography of the Sonoran Desert despite its rich cultural diversity and species richness. I used a combination of ecoinformatics, ethnobotanical, and archaeological data sources to quantitatively assess the impacts of pre-Columbian, and in some cases, more recent, human-mediated dispersal of food plants on the Sonoran Desert landscape. I found that (i) food plants do fill more of their potential geographic ranges than their un-used congeners, and that polyploidy, growth form, and life form are correlated with range filling and past food usage. I also found that (ii) both pre-Columbian and contemporary human population presence are correlated with relative food plant species richness. Thus, both past human food use and contemporary human activities may have influenced the geographic distribution of food plants at regional scales as well as species richness patterns. My research emphasizes that there is an interplay between ecological and anthropogenic processes, and that, therefore, humans must be considered as part of the landscape and included in ecological models. / Dissertation/Thesis / Supplemental Raster Files / Supplemental Spreadsheet Files / Masters Thesis Plant Biology and Conservation 2019

No description available.

Seed dispersal by caching rodents is a context-dependent mutualism in many systems. Plants benefit when seed remaining in shallow caches germinates before being eaten, often gaining protection from beetles and a favorable microsite in the process. Caching in highly unfavorable microsites, conversely, could undermine the dispersal benefit for the plant. Plant invasions could disrupt dispersal benefits of seed caching by attracting rodents to the protection of a dense invasive canopy which inhibits the establishment of native seedlings beneath it. To determine whether rodents disproportionately cache seed under the dense canopy of an invasive grass in southeastern Arizona, we used nontoxic fluorescent powder and ultraviolet light to locate caches of seed offered to rodents in the field. We fitted a general habitat-use model, which showed that disproportionate use of plant cover by caching rodents (principally Chaetodipus spp.) increased with moonlight. Across all moon phases, when rodents cached under plants, they cached under the invasive grass disproportionately to its relative cover. A greenhouse experiment showed that proximity to the invasive grass reduced the growth and survival of seedlings of a common native tree (Parkinsonia microphylla) whose seeds are dispersed by caching rodents. Biased dispersal of native seed to the base of an invasive grass could magnify the competitive effect of this grass on native plants, further reducing their recruitment and magnifying the effect of the invasion.

abstract: Though cities occupy only a small percentage of Earth's terrestrial surface, humans concentrated in urban areas impact ecosystems at local, regional and global scales. I examined the direct and indirect ecological outcomes of human activities on both managed landscapes and protected native ecosystems in and around cities. First, I used highly managed residential yards, which compose nearly half of the heterogeneous urban land area, as a model system to examine the ecological effects of people's management choices and the social drivers of those decisions. I found that a complex set of individual and institutional social characteristics drives people's decisions, which in turn affect ecological structure and function across scales from yards to cities. This work demonstrates the link between individuals' decision-making and ecosystem service provisioning in highly managed urban ecosystems. Second, I examined the distribution of urban-generated air pollutants and their complex ecological outcomes in protected native ecosystems. Atmospheric carbon dioxide (CO₂), reactive nitrogen (N), and ozone (O₃) are elevated near human activities and act as both resources and stressors to primary producers, but little is known about their co-occurring distribution or combined impacts on ecosystems. I investigated the urban "ecological airshed," including the spatial and temporal extent of N deposition, as well as CO₂ and O₃ concentrations in native preserves in Phoenix, Arizona and the outlying Sonoran Desert. I found elevated concentrations of ecologically relevant pollutants co-occur in both urban and remote native lands at levels that are likely to affect ecosystem structure and function. Finally, I tested the combined effects of CO₂, N, and O₃ on the dominant native and non-native herbaceous desert species in a multi-factor dose-response greenhouse experiment. Under current and predicted future air quality conditions, the non-native species (<italic>Schismus arabicus</italic>) had net positive growth despite physiological stress under high O₃ concentrations. In contrast, the native species (<italic>Pectocarya recurvata</italic>) was more sensitive to O₃ and, unlike the non-native species, did not benefit from the protective role of CO₂. These results highlight the vulnerability of native ecosystems to current and future air pollution over the long term. Together, my research provides empirical evidence for future policies addressing multiple stressors in urban managed and native landscapes. / Dissertation/Thesis / Doctoral Dissertation Plant Biology 2014

No description available.

In this dissertation, I examine the Sonoran Desert trilogy by Kathleen Alcalá through the lens of post-oppositional theory as developed by AnaLouise Keating. Moving beyond the use of post-oppositional theory to analyze non-fiction works, I apply this theory instead to the fiction of Kathleen Alcalá—whose work appears in such anthologies as The Norton Anthology of Latino Literature. Alcalá, though well published, is underrepresented in contemporary literary criticism, as can be seen by the only eight entries under her name in the MLA International Bibliography. Therefore, I have chosen her most significant fiction work, her trilogy about the Sonoran Desert, as the perfect text upon which to map post-oppositional theory. Through analysis of her three novels, I show that her work is an ideal example of post-oppositionality in action and that her characters act as post-oppositional revolutionaries and prophets within the pages of the text. The first chapter outlines the parameters of the project. In Chapter 2, I argue that post-oppositionality can be seen in Alcalá through gender bending, looking at the characters of Membrillo and Manzana, Corey, and Rosalinda. In Chapter 3, I argue that the characters of Estela, La Señorita, and Magdalena are enacting post-oppositionality through their transcendence of traditional women's roles in sexuality. In Chapter 4, I argue that the female characters of the novels act as revolutionaries through their political and social agency—reaching out to other characters through such work as educating and writing. In Chapters 5 and 6, I feature my interviews with Alcalá and Keating, who were generous enough to speak with me over Zoom during lockdown. Finally, in the conclusion chapter, Chapter 7, I examine how post-oppositionality in the novels prepares the reader for post-oppositional action in reality. Throughout all of these chapters, I rely on other theories and historiographies such as gender theory (Judith Butler, Foucault, West and Zimmerman, etc.), the history of women's sexuality, and the roles of women in nineteenth century Mexico (looking especially at the works of Nancy LaGreca and Anna Macías).

Many plants are not commercially produced due to a lack of accessible information on their horticultural requirements and landscape potential. Members of the Legume Family (Leguminosae) are often conspicuous components of the vegetation of arid and semi-arid subtropical regions. Many of these plants are suitable for landscaping use in areas suited to their cultivation. Coursetia glandulosa, Erythrina flabelliformis, Eysenhardtia orthocarpa, Haematoxylon brasiletto, Lysiloma watsonii, Pithecellobium mexicanum, and Sophora arizonica are woody legumes native to the Sonoran Desert region which offer a variety of form, texture, color and function. All of these plants grow readily from scarified seed. E. flabelliformis and E. orthocarpa are easy to propagate from stem cuttings. Some irrigation is necessary for establishment and reasonable growth in the landscape. Maintenance and pests are minimal. Freezing temperatures are the primary limiting factor to several of the plants. S. arizonica is slow growing and is prone to rot in the nursery.