Collaborative Research: Gateway to North America--the Great American Biotic Interchange (GABI) in Mexico and Origin of C4 Grassland

美洲之间动物运动的历史模式对了解当前的生态系统和自然资源至关重要。美洲生物大交换（GABI）是南北美洲陆地动物运动的一个非常重要的历史事件，由300万年前巴拿马地峡的出现引发。地峡的形成极大地改变了全球海洋环流、气候和美洲生态系统。大型动物，如巨型地懒、甲雕齿兽和恐鸟向北移动，成为北美冰河时代生态系统不可分割的一部分。北美像大象的象鼻兽、马、鹿、骆驼和食肉动物扩展到南美洲，并引发了该大陆最近一次大规模的本土动物灭绝。一个美墨联合小组将调查墨西哥中部这些事件发生的时间和规模，这是GABI脊椎动物和植物化石知识的一个关键空白。将长期化石记录与古环境分析相结合，可以更详细地重建导致今天美洲生物多样性模式的生态系统重组事件。该项目的更广泛影响包括西班牙语和英语博物馆展览和数字媒体的发展，以及为STEM领域中代表性不足的群体的学生提供研究培训机会。一个由脊椎动物古生物学家、构造地质学家、功能形态学家、植物岩植物学家和稳定同位素地球化学家组成的团队将在墨西哥中部进行实地调查，利用放射性测年、化石哺乳动物生物地层学和磁地层学建立一个综合的区域年代学框架，以记录GABI移民的演替。他们将利用植物岩评估相关的植被变化，并利用哺乳动物牙釉质和古土壤碳酸盐的同位素分析，量化食草动物饮食与北美C4植被起源、区域气候和水文循环之间的关系。广泛的洲际哺乳动物分布模式将使用网络分析来量化深时间生物地理连通性。研究结果将用于验证主要迁移类群的系统发育关系、向高纬度地区扩散的时间和延迟以及区域C4草地扩张的气候和环境影响等假设。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Historical patterns of animal movements between the Americas are crucial to understanding current ecosystems and natural resources. The Great American Biotic Interchange (GABI) is a highly significant historical event of land animal movements between North and South America, triggered by the emergence of the continent-bridging Isthmus of Panama three million years ago. Isthmus formation substantially modified global ocean circulation, climate, and American ecosystems. Large animals such as giant ground sloths, armored glyptodonts, and terror birds moved northward and became an integral part of North American Ice Age ecosystems. North American elephant-like gomphotheres, horses, deer, camels, and carnivorans expanded into South America and triggered the most recent large mass extinction of native animals on that continent. A joint U.S.-Mexico team will investigate the timing and magnitude of these events in central Mexico, a critical gap in knowledge for GABI vertebrate and plant fossils. Integration of long-term fossil records with paleoenvironmental analysis will permit a more detailed reconstruction of the ecosystem reorganization events that led to today’s biodiversity patterns in the Americas. Broader impacts of the project include the development of Spanish and English museum exhibits and digital media, and research training opportunities for students from groups that are underrepresented in STEM fields.A team of vertebrate paleontologists, structural geologist, functional morphologist, phytolith botanist, and stable isotope geochemist will conduct field investigations in central Mexico to establish an integrated regional chronological framework using radiometric dates, fossil mammal biostratigraphy, and magnetostratigraphy to document succession of GABI immigrants. They will assess associated vegetation change using phytoliths and quantify relationships between herbivore diets and C4 vegetation origin, regional climate, and hydrological cycles in North America using isotope analysis of mammalian dental enamel and paleosol carbonates. Broad inter-continental mammal distributional patterns will be contextualized using network analysis to quantify deep-time biogeographic connectivity. Findings will be used to test hypotheses regarding phylogenetic relationships of key immigrant taxa, timing and delay in dispersal to high latitude regions, and climatic and environmental implications of regional C4 grassland expansion.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.