IRFP: Assessing the Role of Ecosystem Structure in Extinction Patterns During the Cretaceous-Paleocene Mass Extinction

国际研究奖学金项目使美国科学家和工程师能够在国外进行9至24个月的研究。该计划的奖励为联合研究提供了机会，并利用独特或互补的设施、专业知识和国外的实验条件。该奖项将支持科里·m·雷德曼博士与克雷格·斯科特博士在加拿大阿尔伯塔的皇家泰瑞尔古生物学博物馆进行为期24个月的研究。威胁现代生态系统的问题之严重，类似于地质时间间隔与物种大灭绝有关；因此，化石记录在理解生态系统对全球范围破坏的反应方面发挥了关键作用。然而，大多数古生态大灭绝研究都集中在测量不同分类类群的灭绝程度或试图确定灭绝的主要非生物原因上。生态系统结构在灭绝事件的传播或抵抗中的作用在很大程度上尚未得到研究。白垩纪-古近纪（K-Pg）大灭绝是地球上最臭名昭著的大灭绝之一。这是由于恐龙的灭绝。尽管发表了大量的论文，但关于K-Pg事件前陆地生态系统的稳定性或健康状况以及灭绝导致的生态系统变化仍存在相当大的争议。本文的目的是利用脊椎动物和花粉的全组合、等级丰度曲线（RACs）定量表征K-Pg灭绝事件前后陆地生态系统结构的变化。RACs是一种生态学技术，用于可视化和定量地描述生态系统中分类群如何分配资源并将这些资源转化为丰度。跨越K-Pg边界的丰度结构的任何变化都表明影响生态系统的过程发生了变化。利用现代和化石生物的生态学研究表明，物种丰度分布随着扰动的频率和幅度而变化。经历频繁扰动的生态系统通常由少数具有广泛栖息地范围或食物偏好的物种（即通才）主导。相比之下，没有经历过频繁扰动的生态系统通常在不同物种之间分配的资源更均匀，每个物种都有非常狭窄的栖息地范围或食物偏好（即专家）。进行这项研究的基本原理是，通过使用不同营养水平的生物（即脊椎动物=初级消费者和次级消费者；花粉=初级生产者）直接分析灭绝前和灭绝后的生态系统，确定在K-Pg边界之前，最新的白垩纪陆地生态系统是否已经处于生态压力之下。

The International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad. This award will support a twenty-four-month research fellowship by Dr. Cory M. Redman to work with Dr. Craig Scott at the Royal Tyrrell Museum of Palaeontology in Alberta, Canada. The magnitude of the problems threatening modern ecosystems resembles those intervals of geological time associated with mass extinctions; for this reason the fossil record provides a critical role in understanding the responses of ecosystems to global-scale disruptions. However, most paleoecological mass extinction studies have focused on measuring the magnitude of extinction among various taxonomic groups or trying to identify the primary abiotic cause(s) of the extinction. The role of ecosystem structure in the propagation of or resistance to an extinction event has largely gone unstudied. The Cretaceous-Paleogene (K-Pg) mass extinction is one of the most infamous mass extinctions in Earth?s history, due to the demise of the dinosaurs. Despite the profusion of publications, considerable controversy remains on the stability or health of terrestrial ecosystems prior to the K-Pg event and the changes in ecosystem caused by the extinction. The objective of the research proposed here is to quantitatively characterize changes in terrestrial ecosystems' structure before and after the K-Pg extinction event, using whole assemblage, rank abundance curves (RACs) of vertebrates and pollen. RACs are an ecological technique used to visually and quantitatively describe how taxa in an ecosystem partition resources and convert these resources into abundances. Any change in abundance structure across the K-Pg boundary would indicate change(s) in the processes that are influencing the ecosystems. Ecological studies utilizing modern and fossil organisms have shown that species abundance distributions change as a result of the frequency and magnitude of perturbations. Ecosystems that have experienced frequent perturbations are typically dominated by a few species that have a wide habitat range or food preference (i.e., generalists). In contrast, ecosystems that have not experienced frequent perturbations typically have resources apportioned more evenly across a diverse array of species, each one having a very narrow habitat range or food preference (i.e., specialists). The rationale for conducting this study is to determine if latest Cretaceous terrestrial ecosystems were already under ecological stress prior to the K-Pg boundary by directly analyzing pre- and post- extinction ecosystems using organisms that occupy different trophic levels (i.e., vertebrates = primary & secondary consumers; pollen= primary producers).