Marine Biotech Fellowship: Population Genetics and Gene Flow in Hydrothemal Vent Communities

深海热液喷口构成了具有专性、多样化、高度专门化的无根生物群落的零星栖息地系统。这些地点为研究深海中的扩散和基因流动提供了一个有希望的机会。先前对这些动物进行的同工酶研究表明，遗传变异水平普遍较低，种群之间的遗传分离迹象有限。最令人惊讶的是，对厚皮虫（一种管状蠕虫）的遗传研究表明种群间几乎没有变异，但它的幼虫传播能力有限，而对嗜热深海贻贝（一种喷口贻贝）的研究表明，尽管喷口种群之间的遗传差异很小，但它们之间的遗传差异却很大。广泛散布的幼虫。由于这两个物种之间存在较大的分类差异，而在厚皮犀中观察到的遗传变异水平较低，上述差异对这些独特群落的种群遗传过程提供了很少的了解。最需要的是在分类上密切相关的物种中有足够的遗传变异，以便在考虑系统发育约束的同时检测群体遗传亚结构。罗格斯大学目前正在进行的研究（NSF OCE-8917211）旨在评估与深海热液喷口相关的软体动物种群的基因流动率和系统关系。来自各种喷口部位的肌脂类和膀胱肌脂类双壳类的等位酶研究已接近完成，而线粒体DNA （mtDNA）的研究才刚刚开始。同时，对管状蠕虫——厚皮虫的研究也在进行中。本项目将以两种主要方式扩展这些正在进行的研究。首先，由于以往的研究发现嗜热芽孢杆菌和厚肺芽孢杆菌的等位酶多态性水平较低，因此将开发一种更灵敏的检测匿名核DNA限制性位点多态性的技术来调查遗传变异。这些数据，连同mtDNA限制性位点数据，将提供这些生物体中位点内和位点之间（母系和双系衍生）遗传变异的全面、多位点分析。其次，本项目将调查巨型孔蛤（Calyptogena magnifica）的遗传变异。黄花菜有大的卵和被认为是非浮游生物的幼虫期。通过将C. magnifica包括在内，这项研究将能够与另一种双壳类动物——嗜热B.进行直接的遗传比较，后者似乎具有浮游营养的幼虫，可能具有更大的传播能力。

Deep-sea hydrothermal vents comprise systems of patchy habitats with obligate, diverse, highly specialized communities of sessile organisms. These sites provide a promising opportunity to study dispersal and gene flow in the deep sea. Previous allozyme studies of several of these animals have revealed generally low levels of genetic variability and only limited indications of genetic separation between populations. What is most surprising is that genetic studies of Riftia pachyptila (a vestimentiferan tube worm), indicated little or no inter-population variation, but it has been suggested to have limited larval dispersal ability, whereas studies of Bathymodiolus thermophilus (a vent mussel) demonstrated significant genetic separation between vent populations in spite of what appears to be a small, broadly dispersing larva. Given the large taxonomic difference between these two species and a low level of observed genetic variation in R. pachyptila, the above discrepancy provides little insight into population-genetic processes in these unique communities. What is most needed is sufficient genetic variation in taxonomically closely related species in order to detect population genetic sub-structuring while at the same time considering phylogenetic constraints. Studies currently underway at Rutgers (NSF OCE-8917211) are aimed at assessing rates of gene flow and systematic relationships of molluscan populations associated with deep-sea hydrothermal vents. Allozyme studies of mytilid and vesicomyid bivalves from a variety of vent sites are nearly completed, and mitochondrial DNA (mtDNA) studies have just begun. Parallel studies of tube worms, Riftia pachyptila, are also underway. This project will expands upon these ongoing studies in two main ways. First, since previous studies found only a low level of allozyme polymorphism in B. thermophilus and R. pachyptila, a more sensitive technique of assaying anonymous nuclear DNA restriction- site polymorphism will be developed to survey genetic variation. These data, along with the mtDNA restriction-site data, will provide a comprehensive, multi-locus analysis of genetic variation, within and between sites (both maternally and biparentally derived) in these organisms. Second, this project will survey genetic variation in the giant vent clam, Calyptogena magnifica. C. magnifica has large eggs and a larval stage that is believed to be non-planktotrophic. By including C. magnifica, this research will be able to make direct genetic comparisons to the results obtained with another vent bivalve, B. thermophilus, which appears to have planktotrophic larvae and presumably greater dispersal abilities.