Dissertation Research: Molecular Systematics and the Evolution of a Novel Red Blood Cell Morphology in Plethodontid Salamanders

论文研究：无齿蝾螈的分子系统学和新型红细胞形态的进化

• 批准号: 0105824
• 负责人: David Wake
• 金额: $ 1万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-07-15 至 2004-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0105824&HistoricalAwards=false
• 关键词: Dissertation; Research; Molecular; Systematics; Evolution

The proposed research will focus on a multidimensional analysis of evolution at different hierarchical levels, from the molecular to the organismal and phylogenetic. The study organisms, plethodontid salamanders of the genus Batrachoseps, are unique among vertebrates in displaying great variation in the proportion of red blood cells in the circulating blood - from nearly all nucleated to nearly all enucleated. The variation appears to be correlated with degree of organismal specialization, in particular with elongation, attenuation, and miniaturization, in a group of organisms that is specialized for semifossorial existence in seasonally dry environments. A complicating factor is the very high genome sizes in these organisms, which raises the possibility that enucleation is a phenomenon associated with a fundamental conflict between large cells, a necessary correlate of large genomes, and small blood vessels, a necessary correlate of miniaturization. The study will investigate the possibility that enucleation is a mechanical outcome of miniaturization, by conducting ecological and morphological studies. In order to proceed it will be necessary to develop a robust phylogenetic hypothesis for the genus, using molecular markers. Mitochondrial genes have already been studied, and there is good resolution of many of the tips of the phylogenetic tree; new work will focus on more conservative nuclear genes and deeper branches in the tree. A phylogenetic hypothesis will permit a comparative biological analysis of this problem area and a determination of whether increases in body size within a miniaturized lineage are accompanied by increases in nucleation levels for red blood cells.The significance of this research lies in the focused effort to study how different levels of organization -- molecular, cellular, organismal, ecological, and phylogenetic -- interact during development to give form and substance to lineages of organisms. A simultaneous investigation of different levels provides a realistic assessment of how evolution proceeds in lineages through time, and permits an assessment of the nature of general adaptation processes and their implications. The study also holds promise for opening new avenues of research on the puzzling phenomenon of increases in genome size, which are so great in these organisms as to strongly effect cellular and organismal levels (the classic C-value paradox).

拟议的研究将侧重于从分子到有机体和系统发育的不同层次上对进化的多维分析。 研究对象是Batrachoseps属的无核蝾螈，它在脊椎动物中是独一无二的，它在循环血液中的红细胞比例表现出巨大的变化——从几乎全部有核到几乎全部去核。 这种变异似乎与生物体的特化程度相关，特别是在季节性干燥环境中专门用于半化石生存的一组生物体中的伸长、衰减和小型化。 一个复杂的因素是这些生物体中非常大的基因组大小，这提出了一种可能性，即去核是一种与大细胞（大基因组的必要关联）和小血管（小型化的必要关联）之间的根本冲突相关的现象。 该研究将通过进行生态和形态学研究，探讨去核是小型化机械结果的可能性。 为了继续下去，有必要使用分子标记为该属开发一个强有力的系统发育假说。 线粒体基因已经被研究过，并且系统发育树的许多尖端都有很好的分辨率；新的工作将集中于更保守的核基因和树中更深的分支。 系统发育假说将允许对这一问题领域进行比较生物学分析，并确定小型化谱系内身体尺寸的增加是否伴随着红细胞成核水平的增加。这项研究的意义在于集中精力研究不同层次的组织——分子、细胞、有机体、生态和系统发育——在发育过程中如何相互作用，为生物体谱系提供形式和实质。 对不同层次的同时研究提供了对谱系中进化如何随着时间的推移进行的现实评估，并允许对一般适应过程的性质及其影响进行评估。 这项研究还有望为基因组大小增加这一令人费解的现象开辟新的研究途径，基因组大小增加在这些生物体中是如此之大，以至于强烈影响细胞和生物体水平（经典的 C 值悖论）。