Collaborative Research: Morphology and Molecules: Diatom Diversification, Extinction, and Dispersal in an Ancient Tropical Lake System

合作研究：形态和分子：古热带湖泊系统中硅藻的多样性、灭绝和扩散内布拉斯加-林肯大学和杜克大学的Sherilyn Fritz和Paul Baker地方性植物群和动物群的起源，那些局限于特定地理区域的起源，已经吸引了自然科学家超过世纪。 地方性种群的演变被归因于多个气候周期带来的生境稳定，这在很长一段时间内促进了遗传多样性的积累，或者归因于大规模干扰事件后的殖民化和广泛辐射。 因此，不同的环境历史轨迹（稳定与不稳定）已经被设定为带来更高水平的地方性和生物多样性。这一高度跨学科的项目将把来自沉积岩芯的化石数据与分子生物地理学相结合，以检验关于热带安第斯山脉的一个主要硅藻谱系-Cyclostephanos andinus复合体-形态和遗传变异的幅度和速度的假设。 中国南方古猿形态多样性和绝灭的微体古生物学分析andinus复合体在过去的~0.4百万年将使用以前从的的喀喀湖，玻利维亚/秘鲁和拉戈Chungará，智利收集的核心进行研究，并与独立的气候变化措施进行比较，在相同的样本分析，以评估环境驱动因素的作用，在模式的演变变化。该项目还将对安第斯高原的多个湖泊进行采样，以描述现代C。andinus种群，并评估种群间的遗传变异，以推断种内进化历史（包括vicariance，扩散和基因流）。 如果流量有限，来自的的喀喀湖和Chungará湖的种群的遗传特征可用于告知分子钟方法，以得出关于多个种群遗传分化时间的假设。 此外，还介绍了C. andinus复合体将被放置在一个更广泛的地理框架内，通过建立所有成员的地理分布的属Cyclostephanos在热带南美湖泊。智力优势和更广泛的影响直接观察化石记录和现代人群的分子遗传特征是研究进化变化的模式和速度的补充方法。 然而，这两种方法很少在一项研究中结合起来调查多样化，扩散和灭绝。 该项目是高度跨学科的，并利用先前的大型湖泊钻探计划所产生的丰富框架来研究进化生物学。 该研究为新的分子遗传学方法与传统的古生物学和生物学工具的联系提供了一个创造性的模型，以研究微生物的进化过程，并将在这个令人兴奋的跨学科前沿培养研究生。 此外，K-12学生和其他公众成员将接触到地质学和分子遗传学的跨学科交叉，项目调查人员积极参与内布拉斯加州的教育和宣传活动。

Collaborative Research: Morphology and Molecules: Diatom Diversification, Extinction, and Dispersal in an Ancient Tropical Lake SystemSherilyn Fritz and Paul BakerUniversity of Nebraska-Lincoln and Duke UniversityThe origins of endemic floras and faunas, those that are restricted to a specific geographic area, have intrigued natural scientists for well over a century. The evolution of endemic groups has been attributed to habitat stability through multiple climate cycles, which fostered the build-up of genetic diversity through long periods of time, or alternatively to colonization and extensive radiation following episodes of massive disturbance. Thus, very different trajectories of environmental history (stability versus instability) have been posited to bring about higher levels of endemism and biodiversity. This highly interdisciplinary project will integrate fossil data from sediment cores with molecular phylogeography to test hypotheses about the magnitude and rate of morphological and genetic variation in a major lineage of planktonic diatom in the tropical Andes, the Cyclostephanos andinus complex. Micropaleontological analyses of morphological diversification and extinction in the C. andinus complex during the last ~0.4 my will be studied using cores collected previously from Lake Titicaca, Bolivia/Peru and Lago Chungará, Chile and compared with independent measures of climate variation analyzed in the same samples to assess the role of environmental drivers in the patterns of evolutionary change. The project also will sample multiple lakes in the Andean Altiplano to characterize the genetic composition of modern C. andinus populations and to assess genetic variation among the populations to infer intraspecific evolutionary histories (including vicariance, dispersal, and gene flow). If flow is limited, genetic characterization of populations from Lake Titicaca and Lago Chungará can be used to inform molecular clock methods to derive hypotheses about the timing of genetic divergences of multiple populations. In addition, the history of the C. andinus complex will be placed within a broader biogeographic framework by establishing the geographic distribution of all members of the genus Cyclostephanos in tropical South American lakes. Intellectual Merit and Broader ImpactsDirect observation of the fossil record and molecular genetic characterization of contemporary populations are complementary approaches for studying the patterns and rates of evolutionary change. Yet these two approaches have rarely been combined in a single study to investigate diversification, dispersal and extinction. This project is highly interdisciplinary and takes advantage of the rich framework generated by a prior large-lake drilling program to investigate evolutionary biology. The research presents a creative model for the linkage of new molecular genetic approaches with traditional paleontological and biogeographic tools to investigate evolutionary processes in microorganisms and will train a graduate student at this exciting interdisciplinary frontier. In addition, K-12 students and other members of the public will be exposed to this interdisciplinary intersection of geology and molecular genetics by the active engagement of project investigators in education and outreach activities in Nebraska.