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

技术说明：该项目的目标是测试三种动物群的变化模型，以响应生物和非生物的强迫在过渡到现代草原生态系统在大平原在过去的4.5我：红皇后，法院小丑，和岛屿生物地理学的平衡理论。在此过程中，我们将回答四个具体的研究问题：1）当地栖息地或气候的长期变化是否控制分类多样性动态？2)与2.5 Ma北方半球冰川作用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（大火山灰）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社区的生态结构？我们将分析多样性动态与现有的数据库中的物种出现在米德盆地，西南堪萨斯在重建当地的古生态，古环境和古气候。 我们将描述生态结构的社区与估计的牙齿尺寸和营养类别重建的碳同位素组成的牙釉质使用激光烧蚀同位素比质谱和一种新的组合的形态分析的基础上高分辨率microCT扫描的身体大小。古食性代理的解释将受到现代物种的同位素和形态测定分析的限制，这些现代物种具有已知的食性和栖息地，这些食性和栖息地来自现有的博物馆藏品和堪萨斯州米德周围草原上的活捕。古环境和古气候重建将基于一套全面的代用指标，这些代用指标是在古土壤碳酸盐和大量沉积物样品上测量的，这些样品是在与已知化石地点和主要火山灰的地层联系中收集的：整体有机质碳同位素比值、叶蜡正构烷烃碳、氢同位素比值、木质素酚比值、植物植硅体组合、碳酸盐块体同位素古温度测定、古土壤元素地球化学和矿物学。古气候代理和同位素数据将比较区域规模的输出，同位素启用古气候模拟在各种强迫。最后，我们将为该地区的现代哺乳动物物种和属构建生态位模型，并使用古气候模型输出来测试气候变化如何可能迫使米德记录中的范围转移和分类更替。非技术性描述：了解现代社区的起源是生态学的一个基本目标，但是，要重建包括地层持续时间在几十万年到几百万年之间的物种的群落历史，就必须从化石记录中获得数据。同样，当从现存物种的活种群和化石种群中获得数据时，关于过去群落的古生态学的推断是最可靠的。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的特征观测时间尺度和方法的差距，以全面了解特定现代社区的长期演变。 面对人为气候变化和地方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紧迫。该项目将研究过去500万年来美国中部草原现代小型哺乳动物群落起源的生态，环境和气候背景。我们将测试生物和非生物因素对长期分类营业额和当地社区的地层序列中的生态变化的影响，使用生态形态学，地球化学，古气候建模和地理学的组合。这个项目将把进化、生态学和古生态学与地球化学联系起来，以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.