ELT Collaborative research: Evolutionary and ecological responses of small mammal communities to habitat and climate change over the last 5 million years

技术描述：该项目的目标是测试在过去4.5My的大平原向现代草原生态系统过渡期间，生物和非生物强迫响应的三种动物变化模型：红皇后、宫廷小丑和岛屿生物地理学的平衡理论。为此，我们将回答四个具体的研究问题：1)当地生境或气候的长期变化是否控制着分类多样性动态？2)与2.5 Ma北半球冰川开始相关的气候变化是否影响群落的多样性动态或生态结构？3)灾难性事件(主要火山灰)如何影响群落的多样性动态和生态结构？4)移民物种如何适应当代群落的生态结构？我们将利用堪萨斯州西南部米德盆地现有的物种出现数据库，分析与重建当地古生态、古环境和古气候有关的多样性动态。我们将利用激光消融同位素比质谱仪和一种基于高分辨率MicroCT扫描的新的形态计量分析组合，通过牙齿尺寸和营养类别重建牙齿釉质的碳同位素组成，来表征群落的生态结构。对古饮食替代物的解释将受到对现代物种的同位素和形态计量分析的限制，这些现代物种的已知食物和栖息地来自现有的博物馆藏品，以及肯塔基州米德市周围草原上的活体诱捕。古环境和古气候重建将基于与已知化石遗址和主要火山灰地层相关的古土壤碳酸盐和块状沉积物样品测量的一套全面的替代指标：块状有机质的碳同位素比率、叶蜡正构烷烃的碳和氢同位素比率、木质素酚比率、植物植硅体组合、碳酸盐聚集同位素古温度测定以及古土壤元素地球化学和矿物学。古气候指标和同位素数据将与不同作用力下的区域尺度的、基于同位素的古气候模拟的结果进行比较。最后，我们将构建该地区现代哺乳动物物种和属的生态位模型，并使用古气候模型输出来测试气候变化可能如何迫使Meade记录中的范围转移和分类更替。非技术描述：了解现代群落的起源是生态学的基本目标，但重建包括地层持续时间在数十万到数百万年之间的物种的群落的历史必然需要化石记录中的数据。同样，当从现存物种的活种群和化石种群的数据中获得信息时，关于过去群落的古生态的推断是最可靠的。尽管生态学和古生态学之间存在逻辑联系，但相对较少的研究弥合了这些学科特有的观测时间和方法上的差距，以实现对特定现代群落长期演变的全面看法。面对人为气候变化和当地社区应对措施的规模和方向的不确定性，弥合这些学科差距的必要性日益迫切。这个项目将研究过去五百万年来美国中部草原上现代小型哺乳动物群落起源的生态、环境和气候背景。我们将利用生态地貌学、生物地球化学、古气候模拟和生物地理学相结合的方法，在当地群落的地层序列中检验生物和非生物因素对长期分类周转和生态变化的影响。该项目将把进化论、生态学和古生态学与生物地球化学联系起来，追踪地质时期现代生态系统的出现。

Technical description: The goal of this project is to test three models of faunal change in response to biotic and abiotic forcings during the transition to the modern grassland ecosystem in the Great Plains over the last 4.5 My: the Red Queen, the Court Jester, and the Equilibrium Theory of Island Biogeography. In doing so, we will answer four specific research questions: 1) Do long-term changes in local habitat or climate control taxonomic diversity dynamics? 2) Does climate change associated with the onset of Northern Hemisphere glaciation at 2.5 Ma impact diversity dynamics or the ecological structure of communities? 3) How do catastrophic events (major ashfalls) impact diversity dynamics and ecological structure of communities? 4) How are immigrant species accommodated in the ecological structure of the contemporary community? We will analyze diversity dynamics with an existing database of species occurrences in the Meade Basin, SW Kansas in relation to reconstructions of local paleoecology, paleoenvironment, and paleoclimate. We will characterize ecological structure of communities with body sizes estimated from tooth dimensions and trophic categories reconstructed from carbon isotope compositions of tooth enamel using laser ablation isotope ratio mass spectrometry and a novel combination of morphometric analyses based on high resolution microCT scans. Interpretation of paleodiet proxies will be constrained by isotopic and morphometric analyses of modern species with known diets and habitats from existing museum collections and live trapping in grasslands around Meade, KS. Paleoenvironmental and paleoclimatic reconstructions will be based on a comprehensive suite of proxies measured on paleosol carbonates and bulk sediment samples collected in stratigraphic association with known fossil sites and major ashfalls: carbon isotope ratios of bulk organic matter, carbon and hydrogen isotope ratios of leaf wax n-alkanes, lignin phenol ratios, plant phytolith assemblages, carbonate clumped isotope paleothermometry, and paleosol elemental geochemistry and mineralogy. Paleoclimate proxies and isotopic data will be compared to output of regional scale, isotope-enabled paleoclimate simulations under various forcings. Finally, we will construct ecological niche models for modern mammal species and genera in the region and use paleoclimate model output to test how climate change may have forced range shifts and taxonomic turnover in the Meade record.Non-technical description: Understanding the origin of modern communities is a fundamental goal of ecology, but reconstructing the history of communities that include species with stratigraphic durations on the scale of hundreds of thousands to millions of years necessarily requires data from the fossil record. Similarly, inferences about the paleoecology of past communities are most robust when informed by data from both living and fossil populations of extant species. Despite the logical connections between ecology and paleoecology, relatively few studies have bridged the gaps in the characteristic observational timescales and methodologies of these disciplines to achieve a comprehensive view of the long-term evolution of specific modern communities. The need to bridge these disciplinary gaps is increasingly pressing in the face of anthropogenic climate change and uncertainty about the magnitude and direction of responses by local communities. This project will examine the ecological, environmental, and climatic context of the origin of the modern small mammal community in the grasslands of the central USA over the last five million years. We will test the effects of both biological and non-biological factors on long-term taxonomic turnover and ecological change in a stratigraphic sequence of local communities using a combination of ecomorphology, biogeochemistry, paleoclimate modeling, and biogeography. This project will link evolution, ecology, and paleoecology with biogeochemistry to trace the emergence of a modern ecosystem over geological time.