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首页> 外文学位 >Population diversity and molecular evolution of selected eastern Pacific sea cucumbers (Class: Holothuroidea) based on mitochondrial DNA.
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Population diversity and molecular evolution of selected eastern Pacific sea cucumbers (Class: Holothuroidea) based on mitochondrial DNA.

机译：基于线粒体DNA的选定东太平洋海参（种群：Holothuroidea）的种群多样性和分子进化。

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摘要

Sea cucumbers (Class: Holothuroidea) are one of six extant classes of the exclusively marine phylum Echinodermata. Unfortunately, these organisms are poorly represented in the fossil record and consequently, the taxonomy and systematics of this class remains problematic. As a preliminary investigation, a molecular phylogeny was constructed focusing on members of the family Cucumariidae from the eastern Pacific. Fourteen hundred nucleotides spanning portions of two mitochondrial genes, encoding the large ribosomal RNA subunit and cytochrome oxidase subunit one, were sequenced from 15 species, representing six families from two orders. A number of important phylogenetic issues were resolved, particularly the relationships among brooding species.;Following this phylogenetic assessment, an analysis of population structure in two species of sea cucumber as a function of their mode of development was undertaken, based on four hundred nucleotides of mitochondrial sequence with presumed homology to the replication control region. Cucumaria pseudocurata exhibits a brooding form of development while Cucumaria miniata passes through a pelagic nonfeeding larval stage lasting up to 14 days. These two species occupy extensive, overlapping ranges along the west coast of North America and populations were sampled between Pescadero Point, California and Juneau, Alaska. Significant geographic structuring of populations was evident in C. pseudocurata indicating limited dispersal. Despite the general trend of strong geographic structuring of populations, there is evidence of significant gene flow between adjacent sites separated by as little as four kilometres of ocean or as much as one hundred kilometres along the coast. The most significant genetic disjunction observed separated Alaskan and Queen Charlotte Island (Haida Gwaii) samples from Vancouver Island and all sample sites further south. The northern population samples were found to contain equal or greater genetic variability compared to many southern sites. The most plausible explanation of this genetic disjunction is therefore survival in northern glacial refugia in addition to the persistence of populations south of the furthest extent of the Cordilleran ice sheet. Presumably, these surviving populations expanded to their present apparently continuous distribution of these externally indistinguishable types following the retreat of the ice sheet. The degree of sequence divergence suggests that this separation existed well prior to the last glaciation and may have been maintained for several million years.;Conversely C. miniata population samples exhibited a panmictic structure over their entire range indicating high levels of gene flow despite a relatively short dispersal phase. These results suggest that mode of development and life history traits have had a profound influence on gene flow.;Finally, mtDNA sequence from C. miniata and C. pseudocurata has revealed a novel tRNA gene arrangement compared to other echinoderms. Analysis of mtDNA indicates this novel arrangement has arisen by a nontandem duplication of an ancestral tRNA gene cluster including putative control elements. Gene sequence analysis indicated potential utility of the tRNAs as a phylogenetic marker at deeper levels than other mitochondrial genes which, in conjunction with tRNA gene order rearrangements, make this a region of promising utility in studies of molecular evolution.
机译：海参（类：Holothuroidea）是仅存在的海洋门棘皮动物的六种现存类之一。不幸的是，这些生物在化石记录中的代表性很差，因此，此类的分类学和系统学仍然存在问题。作为初步调查，我们建立了一个分子系统学，重点研究了来自东太平洋的葫芦科的成员。从两个物种的六个家族的15个物种中测序出跨越两个线粒体基因的1400个核苷酸，它们分别编码大的核糖体RNA亚基和细胞色素氧化酶亚基。解决了许多重要的系统发育问题，特别是育雏物种之间的关系。在进行系统发育评估之后，基于两种海参的400个核苷酸，对两种海参的种群结构进行了分析，并对其生长方式进行了分析。与复制控制区具有同源性的线粒体序列。 Cucumaria pseudocurata表现出一种育雏形式，而Cucumaria miniata则通过上层非摄食幼虫期持续长达14天。这两个物种在北美西海岸沿途分布广泛且重叠，在加利福尼亚州佩斯卡德罗角和阿拉斯加朱诺之间采样了种群。假单胞菌明显具有明显的种群地理结构，表明散布有限。尽管总体上存在着人口地理结构强劲的趋势，但有证据表明，在相距仅四公里的海洋或沿海岸的一百公里处隔开的相邻位点之间存在大量基因流。观察到的最重要的遗传分离是从温哥华岛和更南端的所有采样点分离出阿拉斯加和夏洛特皇后岛（海达瓜）的样本。与许多南部地区相比，发现北部地区人口样本具有相等或更大的遗传变异性。因此，这种遗传分离的最合理的解释是，除了在山脉冰原最南端的种群持续存在之外，在北部冰川避难所还可以生存。据推测，这些幸存的种群随着冰盖的撤退而扩展到了这些外部无法区分的类型的当前明显的连续分布。序列差异程度表明这种分离早在最后一次冰期之前就已经存在，并且可能已经维持了几百万年。弥散期短。这些结果表明，发育方式和生活史特征对基因流动有深远的影响。最后，与其他棘皮类动物相比，小C. miniata和C. pseudocurata的mtDNA序列揭示了一种新颖的tRNA基因排列。 mtDNA的分析表明，这种新的安排是由祖先的tRNA基因簇的非串联复制（包括假定的控制元件）引起的。基因序列分析表明，tRNA在比其他线粒体基因更深的层次上作为系统发生标记的潜在用途，再加上tRNA基因顺序的重排，使其成为分子进化研究中很有希望的用途。

著录项

  • 作者

    Arndt, Allan David.;

  • 作者单位

    Simon Fraser University (Canada).;

  • 授予单位 Simon Fraser University (Canada).;
  • 学科 Biology Ecology.;Biology Zoology.
  • 学位 Ph.D.
  • 年度 1996
  • 页码 269 p.
  • 总页数 269
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 生态学（生物生态学）;动物学;
  • 关键词

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