Kinships And Genetic Differentiations Of The Three Sand Plants Of Artemisia

A. halodendron Turcz.ex Bess,A. intramongolica H.C.Fu and A. ordosica Krasch. are subshrub belonging to genus Artemisia of Compositae. They are edificators or dominant species of sand vegetation, important fixation plants and have played an important role in desert eco-environment protection. The three species have close kinships and quite similar morphological characteristics. The research of their kinships redounds to probe into the phylogeny of section dracunculus of genus Artemisia and provide more molecule-level proofs for the classification among the species. In this paper, the tree species were studied by ISSR makers being combined with anatomic characteristics and environmental factors, the results were as follows:1. The three species had high genetic polymorphism in both species level or in population level. In population level, the sequence of polymoiphic loci percentage was: A. intramongolica > A. ordosica > A. halodendron. The sequence of species level was the same, but the values were very close to, only A. intramongolica slightly higher. Nei's gene diversity index (H) and Shannon index(I) in both species level or in population level, the sequence all were: A. halodendron > A. ordosica > A. intramongolica, opposite to polymoiphic loci percentage. It indicated that A. halodendron had lower polymorphism and higher evenness, A. intramongolica was contrary. The genetic differentiation among populations (Gst) of the tree species were: A. halodendron Gst=0.1041, A. intramongolica Gst=0.0757, A. ordosica Gst=0.0768, it indicated more variations existed within the populations.2. The cluster analysis on 17 geographical populations of the three species demonstrated that the populations of every species were clustered together respectively to three branches, it reflected the definite genetic differentiation among the species. To the relations of the species, the branch of five populations of A. ordosica were clustered together with the branch of seven populations of A. intramongolica firstly, and then with the populations of A. halodendron. It indicated that kinships were nearer between A. ordosica and A. intramongolica. The cluster analysis on the species level demonstrated the same results.3. According to the anatomic characteristics,the leaves and foliage branch of the three species were coincident, reflected that they had quite close kinships. The thick upper and lower cuticle and the big ratio of the palisade mesophyll to spongy mesophyll indicated that the three species had strong drought-resistance ability.4. Analyzing the correlation between the anatomic characteristics and environmental factors to the A. halodendron and A. ordosica , the result showed that: 1) With an decrease of annual precipitation, upper cuticle thickness of the A. halodendron increased, indicated the upper cuticle thicken with the drought to decrease the dissipation for water. 2) The lower cuticle thickness, both of the A. halodendron and A. ordosica tended to thicken with the temperature decrease. The leaf thickness of A. ordosica also had the same tendency. 3) The palisade mesophyll thickness of the A. halodendron tended to thicken with the growth season precipitation decrease and the ratio of medulla to stem increase with the wetness index increase, these reflected the adaptability to water. 4) It was the positive correlation between diameter of basal foliage branch of the A. ordosica and the mean temperature of the warmest month. 5) With the decrease of the temperateness, the cortex thickness of foliage branch of the two species thicken, indicated the coldness made cortex thicken. 6) According to the coefficients of determinant (R2), the value was high only in the upper cuticle thickness and the annual precipitation for the A. halodendron, the diameter of basal foliage branch and the mean temperature of the warmest month for the A. ordosica, it indicated the rule was obvious in the two aspect.