Bouteloua eriopoda (Torr.) Torr., also known as black grama, is a perennial bunchgrass native to arid and semiarid ecosystems in the southwestern region of North America. As a result of anthropogenic climate change, this region is predicted to increase in aridity and experience more frequent extreme drought and extreme wet years. This change in precipitation will no doubt affect black grama; however, few studies have investigated how the specific structural components of this grass will respond. The purpose of this study was to examine the effects of years since start of treatment and annual precipitation amount on tiller and stolon densities, and to test for interaction between the two predictor variables. Additionally, the effects of annual precipitation on ramets and axillary buds were investigated. By using 36 experimental plots that have been receiving drought, irrigated, or control treatments since 2007, tiller density was the most responsive component to both annual precipitation amount and years since start of treatment. Years since start of treatment and annual precipitation amount also had a statistically significant interaction, meaning the effect of precipitation amount on tiller density differs depending on how many years have passed since treatments began. Stolon density was the second-most responsive component; the predictor variables were found to have no statistically significant interaction, meaning their effects on stolon density are independent of one another. Ramet density, ramets per stolon, and axillary bud metabolic activity and density were found to be independent of annual precipitation amount for 2021. The results indicate that multiple-year extreme wet and multiple-year extreme dry conditions in the Southwest will both likely reduce tiller and stolon densities in black grama patches. Prolonged drought conditions reduced tiller and stolon production in black grama because of negative legacies from previous years. Reduced production during prolonged wet conditions could be due to increased competition between adjacent plants.

In the face of the sixth mass extinction on Earth, with the flowering plant family Cactaceae assessed as the fifth most endangered plant or animal family by the International Union for the Conservation of Nature (IUCN), it is imperative that all available tools be used to understand the biodiversity, habitat suitability, climate change impacts and population viability of cacti. Within the Cactaceae, Mammillaria Haw and the closely related genus Cochemiea (K. Brandegee) Walton of Baja California, Mexico, are species-rich, with 46 regionally endemic taxa, 12 of which have been assessed as threatened or endangered by the IUCN. This study clarifies the evolutionary relationships in the Mammilloid clade, a complex and species-rich clade in tribe Cacteae, and generic circumscription of the genera Mammillaria Haw. and Cochemiea (K. Brandegee) Walton, estimates divergence times, diversification rates and ancestral ranges and explores habitat suitability and the risk of extinction of a representative species within these genera. The r species, Cochemiea halei (K. Brandegee) Walton, a narrowly distributed island endemic, is assessed using species distribution modeling (SDM) and population viability analysis (PVA). SDM in this study includes projections to two climate change scenarios over the next century, using four representative particle concentration pathways, and the PVA uses habitat-specific deterministic and stochastic models. The results of molecular phylogenetic analyses of the Mammilloid cladde restore the genus Mammillaria to monophyly via new combinations in the genus Cochemiea. The taxa in this study are shown to be of recent origin resulting from rapid diversification and radiation. Geological and climatic forces at multiple scales appear to be responsible for the high degree of biodiversity and endemism of these cacti. SDM shows that C. halei is likely to be stranded in its fragmented island habitat, has a facultative adaptation to ultramafic soils, and faces a 21%–53% contraction of its range on the islands under climate change scenarios. PVA suggests that C. halei is at increased risk of extinction in response to slight decreases in fecundity and persistence. In general, the perspectives in this dissertation fill several gaps in our prior knowledge of the evolution, biogeography, and conservation pressures of an important, species-rich group of cacti, occurring in a region of high biodiversity and endemism.

The Phoenix Zoo, also known as the Arizona Center for Nature Conservation (PZ), is an Association of Zoos and Aquariums (AZA) accredited zoological institution and among largest-nonprofit, privately-owned zoos in the United States (Smith, 2020). Located within Papago Park in Phoenix (Maricopa County), Arizona, adjacent to the Desert Botanical Garden (DES), the two combine to bring environmental awareness to the Phoenix Metropolitan Region. While the DES specializes in botanical presentation, the ACNC focuses on zoological education. Whereas the flora of DES is well known, that of ACNC has yet to be completely documented. Given its role as a center for public engagement and education, documenting and mapping the floristic diversity of the Phoenix Zoo provides updated botanical information and occurrence records, an important component of understanding biodiversity for the Phoenix area. Between the fall of 2017 and the Spring of 2021, the grounds of the ACNC were walked within the 2-mile perimeter and surrounding exterior within Papago Park. Plant specimens and photographs were collected and archived for later identification using various botanical keys. Species names were verified through updated botanical databases such as Tropicos.org and worldfloraonline.org and compiled into a checklist. A total of 706 species have been identified, and of those 548 specimens have been collected as specimen vouchers. Of these, 120 are of taxa known to be native to the Phoenix Salt River Valley. While approximately 79 of those previously listed taxa native to Papago Park were either not found during this study or were extirpated from the grounds of the ACNC during urbanization of the region. There are 586 exotic taxa, some are common cultivars, while others are new to the region. Data for this survey is publicly available on SEINet, a regional network of North America herbaria (https://swbiodiversity.org/seinet/), as georeferenced voucher specimens, human observations, and photographs. Data is also partially duplicated through the iNaturalist platform (iNaturalist.com).

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.

The remarkable conservation of molecular and intra-/inter-cellular pathways underpinning the fundamental aspects of sugar partitioning in two evolutionarily divergent organisms – a non-vascular moss Physcomitrella patens and a vascular cereal crop Oryza sativa (rice) – forms the basis of this manuscript. Much of our current knowledge pertaining to sugar partitioning in plants mainly comes from studies in thale cress, Arabidopsis thaliana, but how photosynthetic sugar is loaded into the phloem in a crop as important as rice is still debated. Even less is known about the mechanistic aspects of sugar movement in mosses. In plants, sugar either moves passively via intercellular channels called plasmodesmata, or through the cell wall spaces in an energy-consuming process. As such, I first investigated the structure of plasmodesmata in rice leaf minor vein using electron tomography to create as of yet unreported 3D models of these channels in both simple and branched conformations. Contrary to generally held belief, I report two different 3D morphotypes of simple plasmodesmata in rice. Furthermore, the complementary body of evidence in arabidopsis implicates plasma membrane localized Proton Pyrophosphatase (H+-PPase) in the energy-dependent movement of sugar. Within this wider purview, I studied the in situ ultrastructural localization patterns of H+-PPase orthologs in high-pressure frozen tissues of rice and physcomitrella. Were H+-PPases neo-functionalized in the vascular tissues of higher plants? Or are there evolutionarily conserved roles of this protein that transcend the phylogenetic diversity of land plants? I show that H+-PPases are distinctly expressed in the actively growing regions of both rice and physcomitrella. As expected, H+-PPases were also localized in the vascular tissues of rice. But surprisingly, H+-PPase orthologs were also prominently expressed at the gametophyte-sporophyte junction of physcomitrella. Upon immunogold labeling, H+-PPases were found to be predominantly localized at the plasma membrane of the phloem complexes of rice source leaves, and both the vacuoles and plasma membrane of the transfer cells in the physcomitrella haustorium, linking H+-PPases in active sucrose loading in both plants. As such, these findings suggest that the localization and presumably the function of H+-PPases are conserved throughout the evolutionary history of land plants.

Acceptance of the plant group Martyniaceae as a distinct family has long been questioned. Previously placed in the family Pedaliaceae, the Martyniaceae have been allied to numerous other families within the order Lamiales. The objectives of this study include the investigation of the placement of the Martyniaceae within the order Lamiales using molecular data (chloroplast DNA sequences), the further examination of the internal relationships of the Martyniaceae using an expanded nuclear and chloroplast sequences data set, and the construction of a taxonomic treatment of the family that includes all published names and taxa in the Martyniaceae. An analysis of the Lamiales using two chloroplast gene regions (ndhF and rps16) reveals that the Martyniaceae should be segregated from the family Pedaliaceae, but is not able to support the placement of any of its putatively-related families as sister to the Martyniaceae. Sequences from 151 taxa of the Lamiales are included in the analysis, including six representatives from the Martyniaceae. An analysis of the Martyniaceae using three chloroplast gene regions (psbA-trnH spacer, trnQ-5'rps16 intergenic spacer, and trnS-trnG-trnG spacer and intron) and the Internal Transcribed Spacer resolves two major clades within the Martyniaceae corresponding to the North American taxa (Martynia and Proboscidea) and the South American taxa (Craniolaria, Holoregmia, and Ibicella). Sequences from all five genera and 15 taxa were included in the analysis. Results from the molecular phylogenetic analyses are incorporated into a revised taxonomic treatment of the family. Five genera and thirteen species are recognized for the family Martyniaceae.

The Juglandaceae (walnuts, hickories, pecans) has one of the best-documented fossil records in the Northern Hemisphere. The oldest modern genus, Cyclocarya, today restricted to China, first appears in the late Paleocene (57 ma) of North Dakota, USA. Unlike walnuts and pecans that produce edible fruits dispersed by mammals, Cyclocarya fruits are small nutlets surrounded by a prominent circular wing, and are thought to be wind- or water-dispersed. The current study provides the first evidence that fossil fruits were different from modern forms in the number and organization of their attachment to reproductive branches, and in their anatomical structure. Unlike the modern genus that bears separate pistillate and staminate flowers the fossil fruits had attached pollen-bearing structures. Unisexual pollen catkins are also present, suggesting the fossil Cyclocarya may have differed from its modern relative in this feature. Like several other plants from the late Paleocene Almont/Beicegel Creek floras, Cyclocarya shows a mosaic combination of characters not seen in their modern counterparts. Fossils were collected from the field, and examined for specimens exposed on the weathered rock surface. Specimens from Almont were photographed with reflected light, while those from Beicegel Creek cut into slabs and prepared by etching the rock matrix in 49% hydrofluoric and re-embedding the exposed plant material in cellulose acetate and acetone to make "peels". Selected specimens are cut out, mounted on microscope slides, and studied with light microscopy. These fossil fruits were studied because they are the earliest fossil evidence of Cyclocarya. They are exceptionally preserved and thus provide critical structural evidence for changes in that occurred during the evolution of plants within this lineage. Because Cyclocarya fruits are winged, they might be assumed to be wind-dispersed. Their radial symmetry does not have the aerodynamic qualities typical of wind-dispersed fruits, and may have been dispersed by water.