Spatio-Temporal Patterns of Taxonomic and Ecologic Diversity of Marine Triassic Bivalve Molluscs of Western North America

9706040 McRoberts I建议对北美西部三叠纪双壳类软体动物动物群进行物种水平的分析，以记录分类学和生态多样性的时空变化，并测试有关导致早中生代双壳类辐射的结构和原因的假设。具体地说，我的目标是在文献、博物馆和野外收藏的基础上建立一个双壳类软体动物物种的多维数据库。每个物种的出现都将根据它的行会成员、相分布、位置和年龄被分配到不同的时间、昆虫、环境、生态和地理类别。以文献为基础的数据库的建设正在进行中，但需要加强，方法是评估博物馆藏品中的大样本中的物种变异性，以及可最好在实地收集的与古环境和土壤学数据有关的其他材料。我建议参观博物馆，参观三叠纪双壳类收藏品的重要储存库(美国地质调查局、加拿大地质调查局、国家自然历史博物馆、美国自然历史博物馆和蒙大拿大学)，并在美国西部和加拿大的几个关键地点(内华达州、爱达荷州和不列颠哥伦比亚省东北部)进行实地考察，这些地方的双壳类几乎是连续分布的。拟议的项目将建立在早中生代双壳类扩张的先前研究的基础上，并将具体解决以下问题：(1)北美双壳类动物群在整个或部分区间内是否存在纬度梯度，如果是，动物群的起源、灭绝和生态结构在多大程度上受纬度的控制？(2)在所有具有不同自生代特征的双壳类群中，是否存在陆上-近海灭绝和起源的趋势，或者这种模式是否仅限于生活习性相似的几个分支？以及(3)不同的双壳类生态在起源和灭绝度量中发挥了多大程度的作用，是否有选择性物种形成或选择性生存的证据？解决这些问题不仅对中生代早期的动物群扩张具有重大意义，而且对确定可应用于其他时期的多样化和灭绝过程也具有重大意义。

9706040 McRoberts I propose a species-level analysis of Triassic bivalve mollusc faunas of western North America to document spatio-temporal changes in taxonomic and ecologic diversity and to test hypotheses regarding the structure and causal factors leading to the Early Mesozoic bivalve radiation. Specifically, I aim to assemble a multidimensional database of bivalve mollusc species based on literature, museum, and field collections. Each species occurrence will be assigned to various temporal, taphonomic, environmental, ecological, and geographical classes based on it's guild membership, facies occurrence, location, and age. Construction of a literature-based database is underway, yet needs strengthening by assessing species variability in large samples available in museum collections coupled with additional material associated with paleoenvironmental and taphonomic data which can best be collected in the field. I am proposing museum visits to important repositories of Triassic bivalve collections (US Geological Survey, Geological Survey of Canada, National Museum of Natural History, American Museum of Natural History, and the University of Montana) and field investigations at several key sites in the western United States and Canada (Nevada, Idaho, and northeastern British Columbia) where bivalves occur abundantly in nearly continuous sequences. The proposed project will build upon a foundation of prior research on the Early Mesozoic bivalve expansion, and will specifically address the questions: (1) is there a latitudinal gradient in North American bivalve faunas through all or part of the interval, and if so, to what degree are originations, extinctions, and ecologic structure of the faunas controlled by latitude? (2) is there a onshore-offshore trend in extinctions and originations among all bivalve groups with different autecology or is the pattern restricted to just a few clades with similar living habits? And (3) to what degree has differing bivalve ecology played a role in origination and extinction metrics and is there evidence for selective speciation or selective survivorship? Resolving these issues bear significant implications not only for the early Mesozoic faunal expansion, but in determining the processes of diversification and extinction that can be applied to other time periods.