Analysis of the spatial and temporal dynamics of marine bivalve evolution: Combining molecular and densely-sampled fossil data

在现代和古代的淡水和海洋环境中，蛤蜊种类繁多，数量众多，目前有9000多种。现代海蛤在经济上非常重要，不仅是作为人类的食物，还因为它们是人类赖以生存的其他动物的食物，比如鱼。尽管具有这种多样性和重要性，但该群体的进化史尚不清楚，该项目将对蛤蜊5亿年的进化史有更详细的了解。该项目将利用来自DNA序列的信息以及来自现代和化石物种的解剖结构来重建进化模式。此外，这些信息将被用于考虑各种关键问题，如该群体的进化速度如何随着时间的推移而变化，以及从DNA序列研究中获得的进化速度信息与从化石研究中收集的信息在多大程度上不同。该项目还将考虑为什么热带地区的蛤蜊物种比极地地区的蛤蜊物种更多样化，以及生态差异如何影响进化速度。这项研究将为本科生、研究生和一名博士后提供培训，研究结果将用于制定以物种灭绝的原因和后果为重点的高中课程计划。本项目旨在利用丰富的海洋双壳类化石记录信息，以及现存物种的遗传信息，重建高度多样化的双壳类进化模式。自寒武纪进化以来，这一类群的物种多样性波动很大，这为考虑如何将化石和现存分类群的信息纳入系统发育研究提供了一个绝佳的机会。该项目还将关注各种生态特征，包括幼虫类型，如何随着时间的推移影响该群体的物种形成和灭绝率。该项目首先将涉及利用基因库中保存的DNA序列信息以及形态学信息，对所有现存双壳类动物家族的关系进行假设。然后，在科级系统发育的基础上，以海洋和化石分类群为重点，建立一个跨越整个双壳类的种级系统发育。将进行测试，以确定应用于遗传和基于化石的系统发育的不同进化模型下多样化率的差异。一个额外的元素是利用这些系统发育来检验关于为什么双壳类，像大多数其他群体一样，表现出纬度多样性梯度的假设。以往对这些多样性梯度的研究主要集中在现存的陆地分类群上。这项研究将提供一个机会，在海洋生物中更详细地考虑这个问题。此外，通过结合化石分类群，该研究将考虑纬度多样性梯度如何随时间变化，增加一个通常不被考虑的重要时间成分。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Clams are diverse and abundant in both modern and ancient freshwater and marine environments, and today more than 9,000 species exist. Modern marine clams are economically very important not only as food for humans but also because they serve as food for other animals that humans depend on, like fish. In spite of this diversity and importance, the evolutionary history of the group is not well understood, and this project will develop a more detailed understanding of the 500-million-year evolutionary history of clams. This project will use information from DNA sequences as well as from the anatomy of modern and fossil species to reconstruct evolutionary patterns. Moreover, this information will be employed to consider various key questions such as how the pace of evolution in the group has varied through time, and further the extent to which information on rates of evolution derived from the study of DNA sequences differs from that information gathered from the study of fossils. The project will also consider why clam species in the tropics are more diverse than those found in polar regions, and how differences in ecology influence rates of evolution. This research will provide training for undergraduates, graduate students, and a postdoctoral scholar, and the results will be used to develop high school lesson plans that focus on the causes and consequences of extinction. This project aims to reconstruct evolutionary patterns in the highly diverse bivalve clade using information from the rich marine bivalve fossil record, along with genetic information from extant species. This group, since it evolved in the Cambrian period, has fluctuated significantly in species diversity and provides an exceptional opportunity to consider how information from fossil and extant taxa can be incorporated into phylogenetic studies. The project will also focus on how various ecological traits, including larval type, have influenced rates of speciation and extinction in the group through time. The project will first involve developing a hypothesis of relationship for all extant bivalve families using information on DNA sequences housed in GenBank, along with information from morphology. Then, building on the family-level phylogeny, a species-level phylogeny spanning all of Bivalvia will be developed with an especial focus on marine and fossil taxa. Tests will be conducted to ascertain differences in diversification rates under alternative evolutionary models applied to genetic and fossil-based phylogenies. An additional element will be to use these phylogenies to test hypotheses on why bivalves, like most other groups, show latitudinal diversity gradients. Previous studies of these diversity gradients have primarily focused on extant terrestrial taxa. This study will provide an opportunity to consider this issue in greater detail in marine organisms. Further, the study, through incorporation of fossil taxa, will consider how latitudinal diversity gradients have changed through time, adding an important temporal component not often considered.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.