Doctoral Dissertation Research: Late Quaternary Paleoenvironments and Biota of Cuatro Cienegas, Mexico

点击翻译按钮获取中文摘要

Much scientific effort has been devoted to understanding the biological mechanisms and environmental conditions that promote the evolution and maintenance of biodiversity. This dissertation research will use sedimentary archives from sinkhole ponds, or pozas, to investigate the Late-Quaternary environmental conditions at North America's hotspot of endemic biodiversity, the Cuatro Ciénegas Valley in the Chihuahuan Desert of Mexico. Sediments from two pozas will be analyzed to reconstruct the vegetation, climate, and aquatic communities of the Pozas Azules region of the Cuatro Ciénegas valley. Long-term environmental stability is a commonly invoked hypothesis to explain the richness of endemic species in the valley. Pollen assemblages in a sediment core recovered from the Cuatro Ciénegas valley in the late 1960s were interpreted as supporting this hypothesis, but new data from a packrat midden and reanalysis of the early pollen work suggest vastly different Pleistocene environmental conditions in the valley. The project will test the hypothesis of long-term environmental stability in Cuatro Ciénegas by analyzing sedimentary evidence of past environmental conditions and aquatic biota in the valley from the Late Pleistocene to the present. AMS radiocarbon dates on charcoal and plant macrofossils will be used to estimate sediment ages; pollen and charcoal in the cores will be analyzed to infer changes in plant communities, fire regimes, and climate; and remains of aquatic organisms such as snail shells and fish scales will be used to elucidate paleopoza community composition. Sedimentary records suitable for paleoenvironmental reconstruction are extremely rare in the arid regions of North America. This research at Cuatro Ciénegas will produce a detailed record of environmental history over the past 14,000 years in a region where few such records exist. Results will be used by the doctoral student to test a long-held hypothesis of environmental stability in Cuatro Ciénegas, and will be relevant to other scientific research as well as to issues of ecosystem management, including fire management. The collection and analysis of modern pollen samples will make possible modern analog analysis of pollen profiles from the cores, and yield data that will be of use to other researchers working in the Chihuahuan Desert. The award will enable a promising student to improve his dissertation research and to establish a strong independent research career.