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生物体和系统发育的不同等级水平的进化的多维分析。在脊椎动物中，这种被研究的生物是蝙蝠属的多齿火蜥蜴，它在循环血液中的红细胞比例表现出很大的差异-从几乎所有的有核到几乎所有的去核。这种差异似乎与生物体的特化程度有关，特别是与伸长、衰减和小型化有关，这类生物体专门用于在季节性干燥环境中的半异体生存。一个复杂的因素是这些生物中非常高的基因组大小，这增加了去核是一种现象的可能性，这种现象与大细胞之间的根本冲突有关，这是大基因组和小血管之间的必要关联，小血管是小型化的必要关联。这项研究将通过进行生态学和形态学研究，调查摘除眼球是小型化的机械结果的可能性。为了继续进行下去，有必要利用分子标记为该属制定一个强有力的系统发育假说。已经对线粒体基因进行了研究，系统发育树的许多末端都有很好的分辨率；新的工作将集中在更保守的核基因和树中更深的分支上。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，并确定在一个小型化的谱系中，个体大小的增加是否伴随着红细胞核水平的增加。这项研究的意义在于集中精力研究不同水平的组织--分子、细胞、组织、生态和系统发育--在发育过程中如何相互作用，赋予生物谱系形式和物质。不同层次的同时调查提供了对进化如何随着时间的推移而在谱系中进行的现实评估，并允许评估一般适应过程的性质及其影响。这项研究还有望为研究基因组大小增加这一令人费解的现象开辟新的途径。基因组大小增加在这些生物体中如此之大，以至于强烈影响细胞和生物水平(经典的C值悖论)。