四种典型海藻的居群遗传结构和系统演化历史研究

IOCAS-IR > 实验海洋生物学重点实验室

	四种典型海藻的居群遗传结构和系统演化历史研究
	李晶晶
学位类型	博士
导师	段德麟 ; 胡自民
	2016-05-25
学位授予单位	中国科学院大学
学位授予地点	北京
学位专业	海洋生物学
关键词	海藻分子系统地理演化古气候波动冰期避难所遗传分化基因流
摘要	本文以北大西洋的常见红藻掌形藻（Palmaria palmata），宽果藻（Mastocarpus stellatus）和西北太平洋褐藻鼠尾藻（Sargassum thunbergii），羊栖菜（Sargassum fusiforme）为研究对象，采用多套分子标记对这四种大型海藻进行系统的居群遗传和进化生物地理学研究，探究历史（如古气候波动）和当前环境因素（如洋流）如何塑造海藻居群遗传结构、多样性时空分布模式和进化历史。主要结果如下：（1）我们利用线粒体cox2-3和叶绿体rpl12-rps31-rpl9（rps）两套标记研究了北大西洋两岸15个掌形藻居群（Palmaria palmata）遗传变异模式和系统演化历史。线粒体标记的单倍型网状图揭示大西洋两岸的掌形藻居群显著分化为两个遗传世系，分化时间大约在更新世中期（0.453 Ma）。掌形藻欧洲沿岸的居群在冰期时残存在多个避难所，长期的异域隔离造成其复杂的居群结构。北美沿岸的居群遗传结构相对简单，主要影响因素为瓶颈效应造成的遗传多样性降低。此外，IMa分析表明北大西洋东西两岸的掌形藻居群之间没有明显的基因交流，说明两岸居群各自处在隔离分化的状态。（2）我们利用核糖体ITS、线粒体cox2-3和叶绿体rbcL-S三套分子标记研究了北大西洋两岸15个宽果藻居群（Mastocarpus stellatus）遗传变异模式和系统演化历史。细胞器标记的单倍型网状图和谱系进化树显示宽果藻内存在两大谱系（mtDNA：C_N，C_S；cpDNA：R_N，R_S），分化时间大约在0.189 Ma（95%HPD：0.083–0.385 Ma）。根据细胞器标记连锁分析，得到三类连锁单倍型：北部型C_N–R_N，南部型C_S–R_S和混合型C_S–R_N。连锁单倍型可将宽果藻分成两组，S组（C_S–R_S）和D组（C_N–R_N，C_S–R_N），分别对应有性及无性繁殖类群。S组只在英吉利海峡及爱尔兰的戈尔韦海湾南部分布；D组主要分布在欧洲北部和加拿大沿岸。F_ST值计算发现D组居群间存在较大的遗传分化。IMa模拟发现北大西洋两岸D组居群之间存在不对称的基因流，方向主要从挪威和戈尔韦海湾流向加拿大沿岸。这些证据表明加拿大沿岸的宽果藻居群是在末次盛冰期后由欧洲沿岸的无性繁殖类群迁移而来。（3）我们利用核糖体ITS2和线粒体cox2-3标记研究了西北太平洋35个鼠尾藻（Sargassum thunbergii）居群的遗传变异模式和系统演化历史。单倍型网状图和谱系拓扑结构表明鼠尾藻居群之间不存在明显的谱系分化。基于不同分组策略（纬度，经度，洋流海域，生物地理学海域，温度）的遗传变异分析（AMOVA）均一致显示大约70%的遗传变异存在于居群内部。距离隔离模型分析表明鼠尾藻居群间的遗传变异与地理距离之间不存在线性关系。migrate模拟分析显示居群之间绝大多数基因流的方向与西北太平洋海流（如黑潮，中国沿岸流）的流向一致，推测海流是塑造西北太平洋鼠尾藻居群遗传结构和时空演化的主要因素。（4）我们利用线粒体trnW-L、cox3和叶绿体rbcL-S标记研究了西北太平洋26个羊栖菜（Sargassum fusiforme）居群的遗传变异模式和系统演化历史。线粒体连锁标记（trnW-L+cox3）单倍型网状图显示羊栖菜居群分化为三个谱系，他们在地理分布上没有重叠：谱系A分布于日本太平洋沿岸南部，谱系B分布于日本太平洋沿岸中部，谱系C分布在日本海、朝鲜半岛和中国沿岸。谱系间的分化时间约在更新世中期（0.858–1.224 Ma）。其中，谱系C还有3个亚谱系，他们的分化时间约在0.106–0.128 Ma之间：亚谱系C1分布日本海，亚谱系C2分布在朝鲜半岛和中国北部沿岸，亚谱系C3分布在中国南部沿岸。居群演化历史分析显示谱系A、谱系B和亚谱系C1没有发生显著的居群扩张，而亚谱系C2和C3的居群扩张趋势明显，时间约在0.26 Ma。羊栖菜谱系分化的主要原因为冰期时海平面下降引起的长时间居群隔离，而现今地质、水文等环境因素阻碍了居群间的基因流，进而促进了谱系间的隔离分化。
其他摘要	We concluded phylogeographic studies of four marine algae, Palmaria palmata, Mastocarpus stellatus from North Atlantic and Sargassum thunbergii, Sargassum fusiforme from Northwest Pacific, using multi-locus markers. The phylogeographic patterns and evolutionary histories was discussed to assess the relative effects of historical (e.g. paleoclimatic oscillation) and contemporary (e.g. ocean currents) factors in shaping popualtion structure and distribution shifts of genetic diversity. (1) Mitochondrial cox2-3 and plastid rpl12-rps31-rpl9 sequences were obtained from 15 Palmaria palmata populations from North Atlantic. The mtDNA cox2-3 haplotype network showed that North Atlantic P. palmata divided into two genetic lineages in association with mid-Pleistocene (0.453 Ma) climate change. Multiple glacial refugia may have existed for European populations and long-term isolation may have contributed greatly to deep genetic differentiation. The North American P. palmata populations are characterized by comparatively low genetic diversity and shallow phylogeographic structure, likely resulting from population bottleneck effect. IMa 2 analysis did not reveal gene ﬂow between the European and North American coasts, indicating long-term isolation. (2) We sampled 15 Mastocarpus stellatus populations from both sides of the North Atlantic and sequenced portion of the nrDNA ITS, mtDNA cox2-3 and cpDNA rbcL-S. Median-joining networks and ML trees inferred from cox2-3 and rbcL-S consistently revealed two gene lineages (mtDNA: C_N, C_S; cpDNA: R_N, R_S), dating to c. 0.189 Ma (95%HPD: 0.083–0.385 Ma). The concatenated cox2-3 and rbcL-S yielded three cytotypes: a northern C_N-R_N, a southern C_S-R_S and a mixed cytotype C_S-R_N, which enabled us to roughly separate samples into D (direct-type life-cycle) and S (sexual-type life-cycle) groups (northern C_N-R_N and mixed cytotype C_S-R_N = D; southern C_S-R_S = S). S group was found only in southern areas (English Channel and southern Galway Bay), and D group was mainly found in northern Europe and northeastern Canada. Pairwise F_ST analyses revealed a high level of genetic differentiation within D group. IMa analyses also revealed asymmetric genetic exchange among European populations and a predominant postglacial trans-Atlantic migration from Norway and Galway Bay to North America. (3) Nuclear internal transcribed spacer-2 and mitochondrial cox3 sequences were obtained from 35 Sargassum thunbergii populations. Several lines of evidence indicate that S. thunbergii is characterized by shallow population structure. Pairwise F_ST estimates and analyses of molecular variance (AMOVA) at various hierarchical levels (latitude criteria, longitude criteria, marine provinces, biogeographical basins and zoogeographical zones) were conducted to elucidate population genetic differentiation. The consistent result was that around 70 percent of genetic variance occurred within sampling localities. Geographic distances do not correlate with population pairwise genetic differentiations. migrate analyses revealed high levels of asymmetric gene flow among S. thunbergii populations, with the numbers of migrants largely corresponding to the directions of oceanic current systems in the Northwest Pacific. Our integrative evidence suggests that the population genetic structure of S. thunbergii was mainly shaped by oceanic currents in the Northwest pacific. (4) We sampled 26 populations of the brown alga Sargassum fusiforme over the entire distribution range and investigated phylogeographic diversity and demographic history using mitochondrial trnW-L, cox3 and plastid rbcL-S sequences. The concatenated mitochondrial markers revealed three major genetic clades (A, B, C), with A and B located in the Japan-Pacific ocean and C located in the Sea of Japan, Korean and Chinese coasts. IMa estimates revealed deep inter-clade divergence in association with the mid-Pleistocene climate changes (c. 0.858–1.224 Ma). The divergence time for the three subclades of clade C was c. 0.106–0.128 Ma: subclade C1 was located in the Sea of Japan; subclade C2 was located in Korea and North China; subclade C3 was located in South China. Clades A and B had relatively long-term stable population size, whereas sub-clades C2 and C3 underwent sudden expansion at c. 0.26 Ma. We synthesize that the population relic of S. fusiforme in isolated marginal seas during the Pleistocene glacial periods contributed most to the deep genetic split, and the present-day geographic and hydrological barriers maintain such kinds of genetic differentiation.
学科领域	海洋生物学
语种	中文
文献类型	学位论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/112546
专题	实验海洋生物学重点实验室
作者单位	中国科学院海洋研究所
推荐引用方式 GB/T 7714	李晶晶. 四种典型海藻的居群遗传结构和系统演化历史研究[D]. 北京. 中国科学院大学,2016.

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