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题名: 柳属的系统学及生物地理学初探-兼论青藏垫柳组及长白柳组的进化及生物地理关系
作者: 陈家辉
学位类别: 博士
答辩日期: 2006-12-26
授予单位: 中国科学院昆明植物研究所
授予地点: 昆明植物研究所
导师: 孙航
关键词: 柳属 ; 青藏垫柳组 ; 长白柳组 ; 叶表皮微形态学 ; 分支系统学 ; 分子系统学 ; 系统演化 ; 生物地理
学位专业: 植物学
中文摘要: 柳属是一个以北温带分布为主的属,除澳洲、南极洲没有自然分布外,其它各洲都有分布。柳属全世界约有520种,我国有275种。 本文从形态学、叶表皮微形态学、分支系统学、分子生物学等方面对柳属Salix的系统学及生物地理学进行了初步研究;对青藏垫柳组sect. Lindleyanae和长白柳组sect. Retusae的进化及生物地理关系进行了研究。并综合多学科资料对柳属的生物地理学进行了初步探讨。主要研究结果为: 1. 叶表皮微形态研究 对40种杨柳科植物的叶表皮微形态特征进行了光学显微镜及扫描电镜的观察。研究表明:柳属的气孔类型多样,可分为平列型,侧列型(又可分为3个亚型),不规则型,环列型。其中不规则型气孔仅见于青藏垫柳组及长白柳组。胞环型气孔仅在杨属、钻天柳属、柳属大白柳组(即心叶柳属)中有发现,叶表皮微形态特征支持将钻天柳属、心叶柳属从柳属中分出来独立成属。青藏垫柳组及长白柳组均具不规则型气孔,是由于二者适应相似的极端的生境还是系统上的近缘仍有待进一步研究。平列型和侧列型则在几乎所有柳属种中都有发现。平列型气孔是柳属种的原始类型,其它的气孔类型均由平列型气孔演化而来。 柳属的叶表皮细胞可分多边形(见于大多数种)和不规则形(仅限少部分种);垂周壁式样可分为平直至弓形(见于大多数种)和浅波状或波状(仅限少部分种);气孔外拱盖内缘为平滑或啮齿-浅波状;角质膜往往具条纹,在不同的种中有条状、鳞片、颗粒、锥形纤维体等腊质纹饰;气孔大小及气孔密度的变化则与生境相关。这些特征虽然对于柳属的系统学没有太大的价值,但是可以作为稳定的鉴定特征。 2. 分支系统学 通过61个广义的形态性状对柳属的主要类群进行了分支分析,结果表明柳属为一个自然类群,钻天柳属和心叶柳属(大叶柳组)从柳属中划分出来独立成属是不合理的。柳属内部的分辨率较低,只有少数的分支得到了50%以上的靴带支持率,其中长白柳组为一个单系并进而与青藏垫柳组构成一个单系分支,说明这两个组有较近的亲缘关系。 分支树低的一致性指数(CI=0.214, 0.245)表明所选的广义形态性状中的非同源性状多,从而影响了系统发育重建的可靠性和准确性。 3.分子系统学 基于叶绿体trnD-T, atpB-rbcL非编码区及 rbcL基因的序列数据对29组38种柳属植物进行了分子系统学研究,基于以上序列的单独分析及联合分析都表明柳属作为一个单系类群得到了很高的靴带支持率,说明对于柳属在属级水平上的细分并不合理,钻天柳属及心叶柳属应重新并入柳属。分析结果还表明,柳属分为两个大支,其中的一支全部为柳亚属(Skvortsov 1968系统)的种,而其中北美的种和旧世界的种又截然分为两支;另一支的基部类群为三蕊柳组,钻天柳属和大白柳组关系密切,处于亚基部位置。而所有皱纹柳亚属和黄花柳亚属的种聚成一个大支处于分支的顶端,其内部分辨率极低,说明这两个亚属有密切的亲缘关系的同时也说明这两个亚属的种可能是辐射分化产生的。分析结果还表明青藏垫柳组和长白柳组都不是单系类群。 分子系统学的研究表明:柳属植物在起源后的早期很可能就有了分化。其中的一支进一步分化出了包括三蕊柳组、钻天柳、大白柳组、皱纹柳亚属、黄花柳亚属的绝大部分柳属类群。而另外还有一支则演化出了柳亚属。 基于我们的研究结果对柳属在亚属等级上的系统进行了补充,我们建议将柳属划分为五个亚属,柳亚属subgen. Salix,三蕊柳亚属subgen. Amygdalina,钻天柳亚属subgen. Chosenia,皱纹柳亚属subgen. Chamaetia和黄花柳亚属subgenus Vetrix。 4. 生物地理学初探 基于形态学、分子系统学、现代分布格局以及地史资料对柳属的生物地理学进行了初步的研究。东亚尤其是喜马拉雅-横断山区是柳属主要的分布和分化中心。柳属起源于亚洲东北部,起源时间可能为早白垩纪晚期。并使用分子钟推测了柳属各主要类群的分歧时间,其结果表明三蕊柳亚属、钻天柳亚属、皱纹柳亚属、黄花柳亚属是柳属中分化最早的类群,并在较短的时间内分化出这些类群。柳亚属则相对分化较晚。 柳属植物在起源后,向东西两个方向传播并最终在北美汇合,南美洲的柳为上新世时南、北美洲相连后才传播过去的;柳属植物在起源后发生了早期分化,其中的一支为柳亚属或其祖先类群,传播到北美的这些原始的柳亚属的类群与旧世界的种没有多少基因交流,经历了相对独立的演化,另一支演化出了三蕊柳亚属,钻天柳组亚属以及占柳属绝大多数种类的皱纹柳亚属和黄花柳亚属。包括青藏垫柳组在内的大部分青藏高原的柳属植物可能是原始的皱纹柳亚属植物在第三纪全球气候变冷时南迁,到达亚洲中低纬度地区,并在中新世左右扩散到我国西南山地高原地区,随着青藏高原的隆升而就地分化出来的。而长白柳组则是北极-第三纪成分南迁,并经过冰期、间冰期的反复作用而形成现在的北极-高山分布格局。因此,青藏垫柳组和长白柳组在起源上应该没有直接的亲缘关。
英文摘要: The genus Salix (Salicaceae) is widely distributed in the world excetp Australia and Antarctic, mainly in temperate zone of North Hemisphere, with about 520 species all over the world and 275 in China. In this paper, we have primary studied and discussed the systematics and biogeography of Salix based on the research findings in the fields of morphology, leaf epidermis, cladistic analysis, molecular systematics. Meanwhile, we have presented some primary results in evolutionary and biogeographical relationships between Salix sections Lindleyanae and Retusae. The most important findings are summarized as follows: 1. Leaf epidermis 42 species of the family Salicaceae were sampled for studying their leaf epidermal characters under light microscope (LM) and scanning electro microscopy (SEM). The results indicated that the types of stomatal apparatus in Salix or Salicaceae were reltively diverse, including paracytic, laterocytic (3 subtypes), anomocytic, cyclocytic stomatal apparatus observed in Salicaceae. Anomocytic stomata was found only in sections Lindleyanae and Retusae, but it was still unclear whether the epidermal similarity of these two sections indicated their similar habitat conditions and/or their same origin in phylogeny. Cyclocytic sotmata was observed only in Populus, Chosenia sect. Urbanianae (i.e. Toisusu Kimura), which to some extent supported the segregation of Chosenia and Toisusu from Salix as two independent genera. While paracytic and laterocytic stomatal types were observed in almost all species of Salix. Paracytic stomata was considered to be primitive in Salix and Salicaceae and other stomata types were derived from this type. The shape of leaf epidermal cells of Salix are mostly polygonal, seldom irregular; The anticlinal walls of epidermal cells are mostly straight to curved, seldom repand and sinuous; The inner margin of the outer stomatal rim was nearly smooth or erose to repand; The cuticular membrane of the leaf epidermis was striated, often with striated, scales, grains or conicoids wax filaments ornamentation; Stomatal size and density varied in response to enviromental factors. Although these characters are of little value to Salix systematics, they are stable enough for diagnostic use. 2. Cladistic analysis of morphological data Sixty-one morphological characters were used for cladistic analysis, the result indicated that Salix is monophyletic and Chosenia and the division of Chosenia and Toisusu (sect. Urbanianae) from Salix as independent genus is unreasonable. But the resolution and support within Salix clade of the topology were relatively poor. Little clades gained over 50% bootstrap value. Sect. Retusae was monophyletic and then formed monophyletic together with sect. Lindleyana , which indicated those two sections probably had a close relationship. The Constant Index of the strict consensus tree was only 0.214 and 0.245, which indicated too many non-homoplasy characters among the character selected for cladistic analysis, and low reliability and veracity of system reconstruction. 3. Molecular systematics Molecular Phylogeny of 29 sections and 38 species of Salix was analyzed based on chloroplast trnD-T, atpB-rbcL noncoding spacer and rbcL gene sequence data separately and collectively. The result revealed that Salix is monophyletic with support of high bootstrap value, and indicated any subdivision of Salix in the generic level was not supportive and acceptable and two genera, Chosenia and Toisusu, should merge into the genus Salix. The research findings indicated that Salix can be divided into 2 main clades, one included all species of subgenus Salix (system of Skvortsov, 1968), but the species from North America and Old World were separated remarkably wthin this clade. While in the other clade, sections Amygdalinae was in the basal position, Chosenia and Urbanianae had close affinity and in the sub-basal position. And all species of subgenus Chamaetia and Vetrix formed a large clade in the top position, and the inner resolution of these calde was very low, which indicated that these two subgenera had a close affinity and they might evolve by radiative speciation. The result also revealed that both sect. Lindleyanae and Retusae were paraphyletic. Molecular systematics findings indicated the ancestor taxa of Salix had experienced divergency soon after they originated and evolved at least two clades. One of them was the ancestor of sect. Amygdalinae, Chosenia, Urbanianae, subgenus Chamaetia and Vetrix. While one another evolved subgen. Salix. Based on moleculars systematic findings we complement the Salix system on subgeneric level, we suggest that Salix divided into five subgenus, subgen. Salix, subgen. Amygdalina, subgen. Chosenia, subgen. Chamaetia, subgen. Vetrix. 4. Primary discussions on biogeographical analysis There are 3 distribution centers in the genus Salix, Esat Asia, Iran-Turanian, Circum-North. Esat Asia especially Himalaya-Hengduan mountain region are distribution center and divergency center of Salix. Moreover, Salix originated in north-east Asia, no later than late Early- Cretaceous. After Salix origined, it was probably diverged into at least two primitive ancestor taxa. One dispersed towrds east and west and finally met in North America, and later those primitive taxa from North America had almost no gene exchange with those of Old World and both of them evolved independently. The Salix of South America was spread from North America in Pliocene when North America and South America was connected; Another primitive ancestor taxa of Salix was furthered evolved out taxa include subgenus Amygdalina, Chosenia, Chamaetia and Vetrix. Ancestor taxa of subgenus Chamaetia moved to south of Eurasia when the global climate became cold in the Tertiary, and dispersal into highlands of South-West China and began their speciation as the uplift of Qinghai-Tibet Plateau started and finally evolved the mostly Salix taxa of Qinghai-Tibet Plateau include sect. Lindleyanae. Taxa which have same distribution pattern with sect. Retusae were of Arctic-Tertiary origin and late spread into middle latitude area of North Hemisphere and move back to high latitude when climate turned warm, after several times of this process the Arctic-Alpine distribution pattern of Retusae and also some other sections were formed. Consequently, sections Lindleyanae and Retusae have no direct affinity, section Lindleyanae have comparatively independent way of origin and dispersal.
语种: 中文
内容类型: 学位论文
URI标识: http://ir.kib.ac.cn/handle/151853/134
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柳属的系统学及生物地理学初探-兼论青藏垫柳组及长白柳组的进化及生物地理关系.陈家辉[d].中国科学院昆明植物研究所,2006.20-25
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