【作者】 王铁娟；

【导师】 杨持；

【作者基本信息】 内蒙古大学 ， 生态学， 2004， 博士

【摘要】 差不嘎蒿(A.halodendron Turcz.ex Bess.)、褐沙蒿(A.intramongolica H.C.Fu)、黑沙蒿(A.ordosica Krasch.)、白沙蒿(A.sphaerocephala Krasch.)、准噶尔沙蒿(A.songarica Schrenk.)、乌丹蒿(A.wudanica Liou et W. Wang)是同属于蒿属龙蒿组的半灌木蒿类，亲缘相近，形态特征十分相似，分布于中国北方的草原区沙地和荒漠区，并成为沙生植被的建群种或优势种，是我国防风固沙的重要植物。它们的分布区具有明显的区域性，在空间上相互替代，成为地理替代分布种。本文从形态、DNA、分布到与环境的适应性进化，对六种沙蒿进行研究，结果如下： 1．六种沙蒿无论是物种水平还是种群水平均具有高的遗传多样性。物种水平的多态位点百分率的大小顺序为：黑沙蒿＞褐沙蒿＞差不嘎蒿＞白沙蒿。种群水平的多态位点百分率的大小顺序为：黑沙蒿＞褐沙蒿＞差不嘎蒿＞准噶尔沙蒿＞白沙蒿＞乌丹蒿。从差不嘎蒿、褐沙蒿、黑沙蒿、白沙蒿来看，大部分的遗传变异存在于种群内。但白沙蒿的基因分化系数(Gst=0.2348)明显地高于差不嘎蒿(Gst=0.1285)、褐沙蒿(Gst=0.1204)、黑沙蒿(Gst=0.1364)。说明白沙蒿的种群间由于隔离的普遍存在以及种群较小，使种群间产生更多的遗传分化。 2．RAPD研究种间亲缘关系有很好的效果。从种间遗传距离来看，乌丹蒿与其它种遗传距离最大，准噶尔沙蒿与白沙蒿的遗传距离较小，黑沙蒿、褐沙蒿、差不嘎蒿的遗传距离很小。所有种种群的聚类分析显示，每个种的各种群均各自相聚，褐沙蒿的各种群首先与黑沙蒿的各种群相聚，然后它们再与差不嘎蒿的各种群聚到一起，表明这三个种有着最近的亲缘关系，且褐沙蒿与黑沙蒿关系更为密切。白沙蒿的各种群聚到一起，它们再与准噶尔沙蒿相聚，表明两者有着很近的亲缘关系。乌丹蒿则自成一支，与其它种关系较远。以种为单位的聚类显示同样的结果。从褐沙蒿与黑沙蒿的种群聚得最近，遗传一致度高达0.9641，且头状花序均小，形态接近来看，认为褐沙蒿作为黑沙蒿的地理亚种更为合适。 3．ITS序列分析的结果表明，六种沙蒿间的ITS序列高度保守，不能反映出它们的进化关系。但说明它们的亲缘关系密切，在蒿属中为较晚分化的类型，在进化过程中还未引起ITS这一保守区域发生多少变异。 4.六种沙篙的花粉较为相似，极面观均为三裂圆形，三孔沟，孔横长，外壁纹饰在光镜下表面颗粒状，在电镜下为排列较疏的刺，刺基外延。花粉形状有所差异，准噶尔沙篙多为长球形，白沙篙为球形、近球形或长球形，黑沙篙多为球形或近球形，褐沙篙多为长球形或近球形，差不嘎篙多为近球形，乌丹篙为近球形。 5.确认了差不嘎篙是草原区东部沙地分布的种，在《中国植物志》和《内蒙古植物志》中记载的差不嘎篙在山西、陕西、宁夏、甘肃及新疆的分布系标本鉴定有误所至。发现了白沙篙在浑善达克沙地的野生分布，通过RAPD分析，浑善达克沙地的锡林浩特种群与毛乌素沙地的榆林种群的遗传距离最近，由此可推测浑善达克沙地的白沙篙可能是鄂尔多斯高原的毛乌素沙地或库布齐沙漠的白沙篙迁移所至。 6.明确了六种沙篙的分布范围，且绘制了它们的分布图，进一步确定了六种沙篙的区系地理成分:差不嘎篙为东蒙古一科尔沁分布种，褐沙篙是浑善达克沙地分布种，黑沙篙为腾格里一鄂尔多斯分布种，白沙篙为戈壁一蒙古种，准噶尔沙篙为中亚种，乌丹篙为科尔沁沙地西部种。 7.沙篙间的地理替代规律为:黑沙篙、褐沙篙、差不嘎篙呈现出从西南向东北的地理替代分布，白沙篙与准噶尔沙篙构成东西向的地理替代分布。乌丹篙由于与另几个种的亲缘关系较远，不做为这几个种的地理替代种。 8.在黑沙篙、褐沙篙与差不嘎篙这一地理替代系列中，黑沙篙在年均温、最冷月均温、年较差、寒冷指数、6一7月降水、湿润指数、水热综合因子、土壤酸碱度、土壤全磷含量上均与另两个种存在着显著差异。黑沙篙向东北被褐沙篙所替代，应该是水热以及土壤因子的综合作用。褐沙篙与差不嘎篙分布区内，主要是5一6月的降水存在着显著差异，也就是生长季前半期的干旱是褐沙篙区别于差不嘎篙一个特征，这也是两者之间发生替代的原因。对于白沙篙与准噶尔沙篙这一对地理替代种，同样是降水的变率是两者发生替代的原因。 9.根据染色体资料和种间的替代关系并结合荒漠化的历史背景，提出所研究的沙篙是从西向东进化迁移的。更多还原

【Abstract】 This paper focused on studing the six sand plants of genus Artemisia L.--A.halodendron Turcz. ex Bess., A. halodendron Turcz. ex Bess., A. intramongolica H. C. Fu, A. ordosica Krasch., A. sphaerocephala Krasch., A. songarica Schrenk. and A. wudanica Liou et W. Wang. They are half-shrub belonging to section Dracunculus of genus Artemisia with close kinships and quite similar morphological characteristics. Distributed in sand of steppe region and desert region in northern China, they are edificators or dominant species of sand vegetation and important wind break and sand fixation plants. Their distributions have remarkable regional characteristics and replace each other in space, and thus become geographical replacement species. The six sand plants were researched in the following aspects: morphological observation, DNA analysis, distribution and adaptive evolution with environment. The results were as follows.1. The six species had high genetic polymorphism in both species level or in population level. In species level, the sequence of polymorphic loci percentage was: A. ordosica > A. intramongolica > A. halodendron > A. sphaerocephala. In populations level, the sequence was: A. ordosica > A. intramongolica > A. halodendron > A. songarica > A. sphaerocephala > A. wudanica. According to A. halodendron, A. intramongolica, A. ordosica and A. sphaerocephala, more variations existed within the populations. But genetic differentiation among populations (Gst) of A. sphaerocephala was 0.2348, higher markedly than A halodendron (Gst= 0.1285), A. intramongolica (Gst= 0.1204), A. ordosica (0.1364). It indicated that: the populations of A, sphaerocephala had more genetic differentiation owing to small populations and universal isolation among populations.2. It was an effective method to research kinships among species by RAPD. According to genetic distances, it was the largest between A. wudanica and others, small between A. songarica and A. sphaerocephala and smaller among A. ordosica, A. intramongolica and A. halodendron. The cluster analysis on the populations demonstrated that the populations of every species were clustered together respectively. The populations of A. intramongolica were clustered together with the populations of A. ordosica firstly, and then with the populations of A. halodendron. It indicated that kinships of this three species were the nearest, and it was nearer between A. intra- mongolica and A. ordosica. The populations of A. sphaerocephala were clustered together with the population of A. songarica. It indicated that kinships of the two species were near. A. wu- danica was an independent branch, so the kinships between A. wudanica and others were far. The cluster analysis on the species demonstrated the same results. A. intramongolica was regarded as geographic subspecies of A. ordosica because of their populations being the nearest according to the cluster analysis, their genetic identity amounting to 0.9641, their small calathide and similar morphological characteristic.3. ITS sequences analysis demonstrated that ITS sequences of six species were soconservative that they couldn’t reflect evolutionary kinships of six plants. But it showed that kinships of six species were close, and the six plants were lately differentiated species in genus Artemisia, so there weren’t more variations in ITS sequence.4. Pollen morphology of six species were similar, all trisected circular shape in polar view, tricolporate. Observed under LM the ornamentation of exine is granular with spinules arranged sparsely and under SEM the basal part of spinule extend. The pollen shapes of the six species were a little different with most A. songarica prolate, A. sphaerocephala spheroidal, subspheroidal or prolate, A. ordosica spheroidal and subspheroidal, most A. intramongolica prolate or subspheroidal, most A. halodendron subspheroidal, A. wudanica subspheroidal.5. It was confirmed that A. halodendron distributed in eastern sand of steppe region. It was wrongly recorded in <<Flora Reipublicae Popularis Si更多还原