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

许多科学工作致力于了解促进生物多样性的进化和维持的生物机制和环境条件。本论文的研究将使用沉积档案从天坑池塘，或pozas，调查晚第四纪的环境条件在北美的热点地方性生物多样性，在墨西哥奇瓦瓦沙漠的Cuatro Ciénegas山谷。将分析两个pozas的沉积物，以重建Cuatro Ciénegas山谷Pozas Azules地区的植被，气候和水生生物群落。长期的环境稳定性是一个普遍援引的假设，以解释在山谷中的特有物种的丰富性。 20世纪60年代末，从夸特罗谢内加斯山谷中采集的沉积物岩心中的花粉组合被解释为支持这一假设，但来自一个食鼠洞的新数据和对早期花粉工作的重新分析表明，山谷中的更新世环境条件截然不同。该项目将通过分析过去环境条件的沉积证据和从晚更新世到现在山谷中的水生生物群来检验Cuatro Ciénegas长期环境稳定性的假设。碳和植物宏化石的AMS放射性碳年代将被用来估计沉积物年龄;花粉和木炭的核心将被分析，以推断植物群落，火灾制度和气候的变化;和水生生物的遗骸，如蜗牛壳和鱼鳞将被用来阐明paleopoza社区的组成。在北美干旱地区，适合于古环境重建的沉积记录极为罕见。Cuatro Ciénegas的这项研究将在一个几乎没有此类记录的地区产生过去14，000年环境历史的详细记录。研究结果将被博士生用来测试Cuatro Ciénegas长期以来的环境稳定性假设，并将与其他科学研究以及生态系统管理问题有关，包括火灾管理。现代花粉样本的收集和分析将使对岩芯花粉剖面进行现代模拟分析成为可能，并产生可供在奇瓦瓦沙漠工作的其他研究人员使用的数据。该奖项将使一个有前途的学生，以提高他的论文研究，并建立一个强大的独立的研究生涯。

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.