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

许多科学努力致力于了解促进生物多样性进化和维持的生物机制和环境条件。本论文的研究将使用天坑池塘(POZAS)的沉积档案来调查北美特有生物多样性的热点地区--墨西哥奇瓦瓦沙漠的Cuatro Cénegas山谷的晚第四纪环境条件。来自两个Poza的沉积物将被分析，以重建Cuatro Ciénegas山谷Pozas Azules地区的植被、气候和水生群落。长期环境稳定性是解释山谷特有物种丰富性的常用假说。20世纪60年代末在Cuatro Cinegas山谷发现的沉积岩芯中的花粉组合被解释为支持这一假说，但来自丛鼠中间地带的新数据和对早期花粉工作的重新分析表明，该山谷的更新世环境条件截然不同。该项目将通过分析从晚更新世到现在山谷中过去环境条件和水生生物群的沉积证据，来检验Cuatro Cénegas的长期环境稳定性假说。将使用木炭和植物宏观化石上的AMS放射性碳测年来估计沉积年龄；将分析岩芯中的花粉和木炭以推断植物群落、火情和气候的变化；将使用蜗牛壳和鱼鳞等水生生物的遗骸来阐明古生物群落的组成。在北美干旱地区，适合恢复古环境的沉积记录极为罕见。Cuatro Ciénegas的这项研究将在一个几乎没有这样的记录的地区，对过去14,000年的环境历史进行详细的记录。结果将被博士生用来检验Cuatro Cénegas长期持有的环境稳定性假说，并将与其他科学研究以及包括火灾管理在内的生态系统管理问题相关。现代花粉样本的收集和分析将使岩心花粉剖面的现代模拟分析成为可能，并产生对在奇瓦瓦沙漠工作的其他研究人员有用的数据。该奖项将使一个有前途的学生提高他的论文研究，并建立一个强大的独立研究事业。

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.