滇韭多倍体分布与起源研究
杨莹
学位类型博士
导师周浙昆 ; 纪云恒
2010-05
学位授予单位中国科学院研究生院
学位专业植物学
摘要多倍化是物种形成的重要方式,自然界普遍存在多倍体物种。本文通过细胞学研究大致覆盖滇韭分布范围的27个居群超过500个体的的细胞学研究,确定滇韭四倍体——二倍体分布式样。通过形态学研究分析不同倍性滇韭的形态差异,探索二倍体与四倍体形态分化。综合形态学和细胞学证据,运用2个叶绿体基因组非编码区片段rpl32-trnL、 psbD-trhT与核基因rDNA ITS序列对滇韭四倍体的起源方式(同源多倍体还是异源多倍体)及起源次数(单次起源还是多次起源)进行探讨。主要研究结果如下: 1.滇韭核型特征:本文对27个滇韭居群的核型进行了研究,其中13个居群为二倍体,14个居群为四倍体,没有发现二倍体与四倍体的共生居群。二倍体核型公式有2n=16m,2n=14m+2sm,2n=12m+4sm三种,四倍体核型核型公式有2n=30m+2sm,2n=28m+4sm,2n=26m+6sm,2n=28m+2sm+2st四种。不同居群的核型表现出较大的对称性和相似性,核型的二型性不明显。滇韭的最长染色体与最短染色体之比均在2以下,核型不对称系数范围在54.70%—57.96%,所有核型类型都属于1A与2A型,属于非常对称的类型。2.滇韭的细胞地理分布格局:西部分布范围内的以二倍体居群占优,而四倍体居群在东部分布区占优势。从垂直分布的范围上看,滇韭分布区范围内海拔较高的滇西北地区以二倍体分布占优势,滇中与滇东海拔相对较低的地区以四倍体分布占优势。。两种倍性相似度很高,从核型上看,滇韭多倍体可能是同源起源的. 3.滇韭二倍体与四倍体的形态分化: 取滇韭地上部分形态变化较大的植株高、叶片宽度、个体的克隆生长状况、花葶数、每个花葶的小花数、外轮花被的长与宽、内轮花被的长与宽、花丝长、小花梗长这11个数值性状参与分析。滇韭二倍体与四倍体并未发生明显的形态分化,从形态学特征看,滇韭应属于同源多倍体。4滇韭四倍体的起源方式与起源次数:基于ITS序列,采用居群取样的策略,对滇韭与同域分布葱属其他种类的系统发育关系进行分析,二倍体与四倍体滇韭作为一个单系得到较高的支持(bp=100%)。因此,滇韭与近缘种类间并不存在杂交,其多倍化应在种内独立发生,属同源多倍体。叶绿体非编码区rpl32-trnL和psbD-trnT联合序列得到27个单倍型,其中3个为二倍体与四倍体共有。排除平行进化的可能后,推测四倍体滇韭至少起源了3次。四倍体的ITS变异式样要少于二倍体,四倍体间可能存在着广泛的基因交流。
资助项目Polyploidy appears to be the most significant mode of sympatric speciation, it is a prevalent phenomenon in species. In this research to investigate the distribution pattern we analysed 27 populations over 500 individuals’ karyotypes and compared morphological characters between different populations to investigate the morphological polymorphism of different ploidy. Parsimony analysis within 2 non-coding loci from chloroplast genome and rDNA ITS, combined the karyotype and morphological results to disscussed the way and the frequency of tetraploids origin. The major results are shown as follows:1. Karyotypes of different populations in A. mairei,27 populations were studied, 13 diploid and 14 tetraploid populations have been detected. No populations have both ploidy coexist. Three karyotype formulas in diploid: 2n=16m,2n=14m+2sm and 2n=12m+4sm; Four karyotype formulas in tetraploid: 2n=30m+2sm,2n=28m+4sm,2n=26m+6sm,2n=28m+2sm+2st. The karyotypes of all populations showed great similarity. Most chromosomes types are “m” and“sm”,only one “st”found in Songming population. The As.K.% ranged from 54.70% to 57.96% .All karyotype found showed original with type 1A or 2A. Based on the evolutionary trend of karyotype is symmetry to asymmetry, A. mairei is very original in karyotype even compared with other species in the genus Allium.2 .The distribution pattern of populations with different ploidy,Both cytotypes occur across a wide range in the distribution area. But the diploid cytotype was rarely found in the east of Yunnan province, and diploid cytotype prefer higher altitude. The tetraploid is extremely common in the east of Yunnan but rarely found in the west, and tetraploid prefer lower altitudes. No correlation found between the distribution patterns and the karyotype asymmetry. Bisides few populations, the karyotype asymmetry in most tetraploid population are similar with diploid, and the smallest karyotype asymmetry found in tetraploid. So based on the karyotype couldn’t found the evolution trend between two poloidy in A. maimei. This result may implied the multiple origins of the tetraploid in A. maimei, some progenitors of tetraploid were distinct, caused no correlation found between two ploidy. Another possibility is the tetraploid spread very quickly after origins, so the change of the karyotype is not obvious. 3. Morphological Polymorphism of different ploidy,The analysis of variation and multiple comparisons with a result of all characters significantly different among /in populations.Characters using numerical taxonomic method Q cluster reveals that ploidy level has little correlation with the morphological variation. The morphological variations in A. mairei are more correlate with Climte and environment. Because the diploids in west Yunnan have more morphological variations. No obvious morphological differentiation between diploid and tetraploid,the tetraploids in A. maimei are autopolyploid from the sight of morphology.4. Autopolyploid and multiple origins of tetraploids in A. mairei,The parsimony analyses of ITS sequence based on the sampling strategy of A. mairei populations with different species of Allium. The strict consensus tree show the diploids and tetraploids of A. mairei to be monophyletic (100% bootstrap). No hybridization between A. mairei and relatives. The result indicates independent polyploidization processes in A. mairei, and support tetraploids in A. mairei are autopolyploid. Based on 27 haplotypes derived form two cpDNA fragments (rpl32-trnL and psbD-trhT), the network analyses showed tetraploids in A.mairei have arisen at least three times. Phylogenetic analyses based on ITS variation types showed the reproductive isolation between diploid and teraploid may not exist.
语种中文
文献类型学位论文
条目标识符http://ir.kib.ac.cn/handle/151853/16124
专题昆明植物所硕博研究生毕业学位论文
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杨莹. 滇韭多倍体分布与起源研究[D]. 中国科学院研究生院,2010.
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