Life Sciences Commons^™

Mitigating The Impacts Of Human Land-Use Change On Biodiversity: With A Focus On Large Migratory Herbivores, Kina Rebekah Murphy

Biology ETDs

Land-use change, commercial over-harvesting of species, and climate change are recognized as the main drivers of biodiversity loss. As a result, it is estimated that 30% of the planet’s biodiversity may go extinct by 2050. This dissertation focuses on how to mitigate the impacts of land-use change on biodiversity. I focus on large migratory herbivores because they are among the most heavily impacted by global change due to their large home range requirements. Habitat fragmentation, illegal hunting, and human-wildlife conflicts are among the biggest threats to large herbivores and result from land-use change. For this reason, my first chapter focuses …

Impacts Of Long-Term Precipitation Manipulation On Hydraulic Architecture, Xylem Function, And Canopy Status In A Piñon-Juniper Woodland, Patrick J. Hudson

Biology ETDs

The Southwestern US is predicted to become hotter and drier, as global climate change forces increasing temperatures and variability in timing and size of precipitation inputs. Drought stress has become more frequent in recent decades, and resulted in massive forest mortality in piñon-juniper woodlands. During recent severe droughts (2000-2003, 2009-2012), piñon pine (Pinus edulis Englem.) suffered disproportionately high mortality compared to co-occurring one-seed juniper (Juniperus monosperma [Engelm.] Sarg.). A large-scale precipitation manipulation experiment was established in a piñon-juniper woodland in central New Mexico to test hypotheses regarding tree survival and mortality with respect to altered water regimes. Our …

Biogeography, Interspecific Introgression, And The Evolution Of Hemoglobin Genes In The High Andes: The Evolutionary History Of The South American Siskins (Spinus), Elizabeth Jane Beckman

Biology ETDs

Landscape features, interspecific introgression, and adaptation work in concert to shape the evolutionary history of a clade. Understanding the independent and cumulative consequences of these evolutionary processes on diversification is critical to revealing the origins of extant biodiversity. Studying these processes within rapid radiations, a significant contributor to global biodiversity, can provide powerful insight into the process of diversification. To assess how diversification is shaped by these evolutionary forces, I examined the biogeographic history, patterns of interspecific introgression and adaptation to high elevation in a recent, rapid radiation of finches, the South American siskins (Fringillidae: Spinus). I found that …

Assessing The Climate Change Vulnerability Of Ecosystem Types Of The Southwestern U.S., Francis J. Triepke, Esteban H. Muldavin, Maximillian M. Wahlberg, Timothy K. Lowrey, Donald A. Falk, Megan M. Friggens, Karen E. Bagne

Biology ETDs

Climate change is challenging scientists and decision-makers to understand the complexities of climate change and to predict the related effects at scales relevant to environmental policy and the management of ecosystem services. Extraordinary change in climate, and the ensuing impacts to ecosystem services, are widely anticipated for the southwestern United States. Predicting the vulnerability of Southwest ecosystems and their components has been a priority of natural resource organizations over the past decade. Supplementing vulnerability assessments in the region with geospatial inputs of high thematic and spatial detail has become vital for supporting local analyses, planning, and decisions. In this context …

Shifts In The Relative Importance Of Competition And Mutualism For Communities And Ecosystems, Lukas P. Bell-Dereske

Biology ETDs

Plant species interact with at least one, likely many, microbial mutualist throughout their life cycles. These microbial mutualists can have strong effects on plant communities and ecosystem processes. Fungal endophytes within the genus Epichloë associate with ~20%–30% of grass species and have been shown to have strong effects on plant communities. Here I described the effect of Epichloë amarillans associated with the dominant grass species, Ammophila breviligulata, on nutrient cycling, below-ground microbial community, and compare the strength of its effects on plant communities to plant-plant competition.

In chapters one and two, I examine the effects of Epichloë on litter …

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.

The Molecular Systematics And Phylogeography Of The Widespread North American Meadow Vole (Microtus Pennsylvanicus), Donavan J. Jackson

Biology ETDs

The climatic and environmental fluctuations of the Quaternary played an integral role in geographic distribution and genetic structure within many organisms today. Understanding how these historical biogeographic events may have partitioned genetic variation throughout the landscape is critical to forecasting the implications of modern climate change and how animals will respond to projected climate shifts. Through geographic and taxonomically comprehensive sampling, we used multi-locus and species delimitation analyses along with niche modeling methods to investigate the evolutionary and biogeographic history of the meadow vole, Microtus pennsylvanicus. The findings of this study highlight the vulnerability and importance that special consideration …

Montane Valley Grassland Plant Communities Are Highly Resistant To Wildfire, Martina M. Suazo

Biology ETDs

Understanding the ecological role of fire in fire-adapted plant communities is of great importance for restoration and preservation; however, limited research has been conducted on the response of upper elevation, C₃ grassland plant communities to wildfire. This study investigates the effects of the Las Conchas wildfire of 2011 on plant community structure and function in the montane valley grasslands of the Valles Caldera National Preserve, Jemez Mountains, New Mexico, USA. Long term monitoring of nine burned and seven unburned grassland sites was used to measure vegetation composition and dynamics both spatially and temporally relative to fire. Results show that …