Genetic Variation And Ecological Differentiation Of Stipa Krylovii And Stipa Breviflora

Molecular ecology and ecological adaptation are research focus of ecology in recent years. Stipa spp. are dominant plants in Europe-Asia steppes and adapt various habitats by abundant intraspecific and interspecific biodiversity. A number of closely related species form a sequential distribution pattern along an environment gradient, so Stipa spp. are ideal plants to study the relationship between genetic diversity and their environment. Stipa krylovii and Stipa breviflora, which is typical representative of section of Leio stipa Dum. and section of Barbatae Junge respectively, are main constructive and dominant species in typical and desert steppes in Northern China respectively. The technique of random amplified polymorphic DNA (RAPD), Nei's index and Shannon index are used to assess genetic diversity of fifteen natural populations of Stipa krylovii and ten natural populations of Stipa breviflora which distribute in Qinghai-Tibet and Inner Mongolian plateau in this paper. The relationships between RAPD variation and geographic distance are estimated using Mantel tests. The results are as follows: 1. The percentage of polymorphic loci is 96.22% between Stipa krylovii populations, while 95.37% between Stipa breviflora populations. The total genetic diversity index of Stipa krylovii and Stipa breviflora population is 0.4447 and 0.3694 using Shannon index. The genetic diversity of two kinds of Stipa are all high, but Stipa krylovii higher than Stipa breviflora. Two kinds of Stipa shows strong adaptation, however, Stipa krylovii stronger.2. Nei's index and Shannon index show the genetic and variation of each Stipa arise among different populations on large regional scale, while different individuals within a population have less genetic and variation.3. On a large scale of Qinghai and Inner Mongolia, the correlation of the genetic distance and geographic distance is significant to Stipa krylovii, however, insignificant to Stipa breviflora. On the district scale,, the correlation of genetic distance and geographic distance among 11 Stipa krylovii population is significant in Inner Mongolia (relatively larger region), but insignificant in Qinghai(relatively smaller region). The correlation of genetic distance and geographic distance is not significant for Stipa breviflora in Inner Mongolia and Qinghai.4. The differentiation index and the gene flow is reducing with the scale shrinking. This shows the differentiation index is small in relative small scale, and larger in relative large scale.