Studies On Kinships, Geographical Replacement Law And Reasons Of The Six Sand Plants Of Artemisia In Northern China

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 <