小麦族系统与进化的研究

NWIPB OpenIR

	小麦族系统与进化的研究
其他题名	Studies on the Systematics and Evolution of Triticeae (Poaceae)
	苏旭
学位类型	博士
导师	蔡联炳
	2005-05-25
学位授予单位	中国科学院西北高原生物研究所
学位授予地点	西北高原生物研究所
关键词	小麦族性状分类价值性状递变趋势分类系统进化关系
摘要	小麦族是禾本科中的经济族，也是分类学上的疑难族，针对该族过去在类群划分和类群进化上的存在问题，本论文特选择了形态学、解剖学、胚胎学、细胞学、以及分子生物学等多学科研究手段，认真分析了宏、微观各方性状的分类价值，对族下类群进行了订正，重新建立了更加合乎自然的小麦族分类系统；同时，全面筛选了具有演化意义的多学科性状，在弄清性状递变趋势的基础上，对族下类群进行了演化水平、亲缘关系及派生渊源的探讨；并且最后还进一步采用分支系统学的方法和原理，对族的大类划分及进化关系进行了新的评判与检验，从而使小麦族系统与进化的研究更趋于准确与科学。通过各科证据的综合研究，小麦族可以分为3亚族、19属，即披碱草亚族、大麦亚族和小麦亚族，其中披碱草亚族含4属、大麦亚族含4属、小麦亚族含11属，原分类系统中的冰草亚族、柱穗麦亚族归并到小麦亚族，原拟鹅观草属划归到鹅观草属。小麦族中以披碱草亚族最原始，大麦亚族较进化，小麦亚族最高级；赖草属于该族原始性较低，小麦属于该族进化程度较高，而其余17属的演化水平则居于该两属之间；披碱草亚族与大麦亚族关系较近、与小麦亚族相对疏远，大麦亚族与小麦亚族同源，可能均起生于原始的披碱草亚族。在研究中，来自各方的证据均起到了不同程度的重要作用。其中，在外部形态上，花序的类型与形状、小穗的数目与育性、小花的形状与枚数等性状具有类群划分的价值，能将小麦族区分为不同的亚族和属，尤其是花序的类型及穗轴同节小穗的数目具有明显的递变趋势，能清晰地判别出族下类群间的进化关系，为演化树系图的绘制奠定了基础；在叶表皮上，具有分类价值的性状主要集中在长细胞的形态、气孔器的体积、短细胞的有无和刺毛的多少等方面，但真正的区分功能不在于亚族、而在于属，特别是其间有些性状如长细胞壁的厚度、副卫细胞的形状、短细胞的排列、以及刺毛的类型等同样具有演化趋势，可以比较容易地判断出族下各个属间的演化关系，只是对于亚族意义不大；在叶横切上，能用于亚族和属区分的性状较多，包括表皮的凹凸程度、下表皮细胞的排列及壁的厚薄、大小型维管束的数目、中肋维管束的横径、大维管束处厚壁组织的着生、以及维管束内鞘细胞的加厚方式等，但具有演化趋势的性状却仅有下表皮细胞的排列、大小型维管束的数目和中肋维管束的横径，这些性状对于族下亚族、特别是属间关系的探讨是缺一不可的；在成熟胚纵横切上，具有类群划分价值的性状有胚芽鞘顶端形态、外胚叶有无、胚长与胚厚之比、胚芽鞘高与基宽之比、胚根鞘实体段长与胚根长之比、第1幼叶维管束数目等，但这些性状一般在属群区分上表现较高的功效，在亚族区分上功效甚微或无，尤其是其间具有明显演化趋势的胚芽鞘顶端形态、胚长与胚厚之比、胚芽鞘高与基宽之比、胚根鞘实体段长与胚根长之比、第1幼叶维管束数目的性状，也仅能将属间演化关系表明清楚，对于亚族仍无能为力；在染色体核型上，染色体长度比、平均臂比、臂比大于1.5的染色体比例以及不对称系数等性状虽对亚族划分失去意义，但对于属群区分却具有价值，可将该族处理为与形态划分相似的不同属，并且还能依据各属所具的进化指数，获得属间进化关系的全面了解；在ITS序列上，基于小麦族18属、52个种的ITS序列构建的最大简约树，不仅形象地表明了小麦族可以区分为与形态划分相似的不同亚族和属，而且还能比较清晰地判定出族下各类群间的演化关系，只是在个别属的亲缘关系上，由ITS序列提供的证据与其它学科的证据尚存在一定差异；在分支系统学上，以雀麦属为外类群、采用PAUP程序对小麦族19属、40类广义形态学性状进行的分支分析，完全可以通过最终获得的最简约严格一致性树反映出来，其结果小麦族是一单系类群，在树系图上该族所展示的类群划分与类群演化跟本论文依据形态学、解剖学、细胞学和分子生物学而获得的结论是基本一致的，从而使传统方式建立的小麦族系统与进化理论在这一学科上得到了应有的检验和印证。所以，在上述多学科证据的协力下，共同揭示了小麦族类群划分及类群演化的自然面目，为本论文小麦族系统与进化的研究划上了圆满的句号。
其他摘要	Triticeae is an economic tribe of Poaceae and also a tribe with questions in taxonomy. Aimed at the existent questions on the classification and evolution of taxa in the past, the dissertation especially selected the multi-subject research methods ranging from morphology, anatomy, embryology, cytology, molecular biology, and carefully analyzed the taxonomic value of macroscopical and microcosmic characters, and revised the taxa below tribe grade. At last, the more natural taxonomic system of Triticeae was newly established in this dissertation. Meanwhile, the multi-subject characters with evolutionary meaning were wholly filtered. On the basis of clarifying the evolutionary trend of characters, the evolutionary level, relationship and derived origin of taxa below tribe grade were discussed. In the end, a judgment about classification of subtribes and evolutionary relationship were newly made and checked, adopting to the method and theory of cladistics. Thus, it made the study on systematics and evolution of Triticeae become more exact and scientific. Through the integrated research on every subject evidence, it is confirmed that the new system is made up of three subtribes and nineteen genera, namely Elyminae, Hordeinae and Triticinae. And Elyminae comprises four genera; Hordeinae contains four genera; Triticinae includes eleven genera; Agropyrinae and Henrardiinae which belong to the original taxomic system are merged into Triticinae and Pseudoroegneria is combined into Roegneria. In Triticeae, Elyminae is the most primitive genus, Hordeinae is more evolutionary and Triticinae is the most advanced; Leymus has the lower aboriginality, and Triticum owns the higher evolutionary grade, while the evolutionary level of other seventeen genera lies between Leymus and Triticum; the relationship between Elyminae and Hordeinae is closer while that between Elyminae and Triticinae is relatively distant. So Hordeinae and Triticinae have the common origin and might have been derived from the primary Elyminae. During the research, the evidence from every aspect all has important and different functions. The external morphology, among which the type and shape of inflorescence, the number and procreation of spikelet, the number and shape of floret and so on are related with the classification of taxa and can differentiate between the different subtribes and genera of Triticeae, especially the type of inflorescence and the number of spikelet on each rachis node have the obvious evolutionary trend and can clearly distinguish the evolutionary relationship of taxa below tribe grade, which establishes the foundation for drawing the sketch map of the evolutionary relationship. Under the leaf epidermis, the characters with taxonomic value are mainly concentrated on these aspects including the modality of long cells, the volume of stomata, the presence or absence of short cells, the number of prickle hairs, etc. They only have the function of distinguishing the genera. In particular, some characters, such as the width of cell walls of long cells, the shape of subsidiary cells, the arrangement of short cells, the type of prickle hairs and so on, and have the evolutionary trend that can easily judging the evolutionary relationship among genera, but the trend above has not much to do with subtribes while with genera. In the transverse section of leaf blades, there are more characters distinguishing the subtribes and genera, such as the protuberant extent of epidermises, the cell arrangement and thickness of cell walls of lower epidermises, the number of large and small vascular bundles, the horizontal diameter of midrib vascular bundles, the inserted status of sclerenchyma jointed to large vascular bundles, the incrassate mode of inner sheath cells and so on. But the characters with the evolutionary trend are only the cell arrangement of lower epidermises, the number of large and small vascular bundles and the horizontal diameter of midrib vascular bundles. Furthermore, these characters have an important effect on discussing the relationship among subtribes, especially genera. On the longitudinal and transverse section of mature embryos, the characters, such as the top modality of coleoptiles, the presence or not of epiblasts, the ratio of the length of embryos to their thickness, the ratio of the height of coleoptiles to the width of their base, the ratio of the length of the solid part of coleorhizas to that of radicles, the number of bundles of the first young leaf and so on, have put up the higher efficacy on distinguishing genera, while they only have the inappreciable or no efficacy on distinguishing subtribes. Especially, these characters with the evolutionary trend, including the top modality of coleoptiles, the ratio of the length of embryos to their thickness, the ratio of the height of coleoptiles to the width of their base, the ratio of the length of the solid part of coleorhizas to that of radicles and the number of bundles of the first young leaf, are merely able to make it clear to explain the evolutionary relationship among genera, but cannot expound the evolutionary relationship among subtribes. For the chromosomal karyotype, the characters with the ratio of the longest chromosome to the shortest, the arm ratio in mean, the proportion of chromosomes with arm ratio>1.5, the index of the karyotypic asymmetry, etc are not related with compartmentalizing subtribes but related with the value of distinguishing genera, and which may divide Triticeae into different genera which are similar to the morphological classification. Meanwhile, we can obtain comprehensive understanding about the evolutionary relationship among genera according to the evolutionary index of every genus. For the internal transcribed spacer sequences, the maximal parsimonious tree based on ITS sequences from 52 species of 18 genera of Triticeae not only visually indicates that Triticeae can be divided into different subtribes and genera which are similar to the morphological classification but also relatively clearly determine the evolutionary relationship among taxa below tribe grade. As a matter of fact, on the relationship of separate genus, there is still stated difference between the evidence provided by ITS sequences and those from other subjects. According to the cladistic analysis, which is carried through forty kinds of generalized morphological characters from 19 genera making use of PAUP programme and chosen Bromus as the outgroup, can completely be reflected by the strict consensus cladogram of the most parsimonious tree ultimately obtained. The result showed that Triticeae was a monophyletic group and the classification and the evolution of taxa set out on the cladogram were nearly consistent with the conclusion acquired by morphology, anatomy, cytology and molecular biology in this dissertation, so the theory on systematics and evolution of Triticeae established by the traditional fashion is generally verified and confirmed on this subject. Therefore, this dissertation reveals the natural face on the classification and the evolution of Triticeae under the cooperation of the evidence from the multi-subject above. Accordingly, it draws the orbicular full stop for the systematics and evolution of Triticeae in this dissertation.
页数	177
语种	中文
文献类型	学位论文
条目标识符	http://210.75.249.4/handle/363003/3214
专题	中国科学院西北高原生物研究所
推荐引用方式 GB/T 7714	苏旭. 小麦族系统与进化的研究[D]. 西北高原生物研究所. 中国科学院西北高原生物研究所,2005.

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