Collaborative Research: Late Quaternary Paleoenvironments of Cuatro Cienegas, Mexico, a Hotspot of Endemism in North America

湖泊和湿地中的沉积物保存了过去2万年来地球气候、植被和生态动态变化的重要证据。在这个项目中，研究人员将研究沉积档案，以记录墨西哥北部奇瓦瓦沙漠Cuatro Ciénegas山谷的生态和环境历史。Cuatro Ciénegas是一个独特的沙漠泉水系统的所在地，该系统支持着北美特有物种的最集中，被拿来与加拉帕戈斯群岛相提并论。Cuatro Cinegas生物群的高度地方性被解释为山谷长期与世隔绝和环境稳定的结果。20世纪70年代分析的沉积岩芯的花粉记录最初被解读为支持这一假说，但最近对原始记录的重新评估，以及附近一处寄居鼠栖息地的新花粉数据，挑战了山谷内环境长期稳定的假设。旧记录的一个复杂之处在于，散装沉积物中早期放射性碳测年的不确定性。这项研究项目将利用两个新的沉积物岩心，其中包含适合AMS测年的宏大化石，以及丰富的花粉和木炭，将提供有关植被和火灾历史的信息。研究人员将通过记录Cuatro Cénegas山谷过去的环境条件，以安全的年代和更高的分辨率来检验Cuatro Cénegas山谷长期稳定的假说。这些岩芯是2008年从Privada Pozas Azules保护区的湿地中发现的，那里有一大批处于不同演替阶段的天坑池塘。Poza Cortado的12.3米剖面跨越了14,000多年，显示出从深水Poza到湿地植被茂盛的沼泽的演替。来自附近Poza Tule的一份侧面资料涵盖了过去约5000年的情况。适合保存花粉的连续沉积环境在北美干旱地区尤为罕见。待分析的沉积物记录将提供奇瓦瓦沙漠晚冰期和全新世条件的重要证据，并提供对北美冰川地区以外发生的环境变化的洞察。Cuatro Cénegas山谷已成为研究生物地理学、生态学和进化论基本问题的天然实验室，这项对长期历史的研究将增加这个自然实验室的价值。研究项目的结果将为古气候学和生物地理学提供信息，并将为许多关于物种形成、共同进化、微生物进化和天体生物学的研究提供关键背景，这些研究侧重于Cuatro Cénegas山谷独特的物种和物种组合。项目成果还将为管理、养护和恢复Cuatro Cénegas的自然资源和特有生物多样性的持续努力提供信息。该研究项目将为几名研究生和本科生以及K-12学生和其他通过项目推广服务的人提供教育机会。该项目由地理学和空间科学计划以及人口和社区生态计划共同支持。

Sediments in lakes and wetlands preserve important evidence of changes in Earth's climate, vegetation, and ecological dynamics over the past 20,000 years. In this project, researchers will study sedimentary archives to document the ecological and environmental history of the Cuatro Ciénegas valley in the Chihuahuan desert of northern Mexico. Cuatro Ciénegas is home to a unique desert spring system that supports North America's highest concentration of endemic species, garnering comparisons to the Galapagos Islands. The high endemism of the Cuatro Ciénegas biota has been explained as a consequence of long-term isolation and environmental stability in the valley. A pollen record from a sediment core analyzed in the 1970s was originally interpreted as supporting this hypothesis, but recent reevaluation of the original record, along with new pollen data from a nearby packrat midden, challenged the assumption of long-term environmental stability within the valley. A complication with the old record is uncertainty over early radiocarbon dates on bulk sediment. This research project will make use of two new sediment cores that contain macrofossils suitable for AMS dating along with abundant pollen and charcoal that will provide information on both vegetation and fire history. The researchers will test the hypothesis of long-term stability in the Cuatro Ciénegas valley by documenting, with secure dating and at higher resolution, past environmental conditions in Cuatro Ciénegas. The cores were recovered in 2008 from wetlands in the Reserva Privada Pozas Azules, which contains a large assemblage of sinkhole ponds, or pozas, in various stages of succession. The 12.3 m profile from Poza Cortador spans over 14,000 years and shows evidence of succession from a deep-water poza to a marsh with emergent wetland vegetation. A profile from nearby Poza Tule covers the last c. 5000 years. Continuous depositional environments suitable for pollen preservation are exceptionally rare in the arid regions of North America. The sediment records to be analyzed will provide important evidence of Late Glacial and Holocene conditions in the Chihuahuan Desert and provide insight into the environmental changes that occurred outside of glaciated regions of North America. The Cuatro Ciénegas valley has become a natural laboratory for studying fundamental issues in biogeography, ecology, and evolution, and this research on long-term history will increase the value of this natural laboratory. The results of the research project will inform paleoclimatology and biogeography, and will provide crucial context for the many studies of speciation, coevolution, microbial evolution and astrobiology that focus on the unique species and species assemblages of the Cuatro Ciénegas valley. Project results will also inform ongoing efforts to manage, conserve, and restore the natural resources and endemic biodiversity of Cuatro Ciénegas. The research project will provide educational opportunities for several graduate and undergraduate students, and for K-12 students and others served by project outreach. This project is jointly supported by the Geography and Spatial Sciences Program and the Population and Community Ecology Program.