Abstract: The genetic differentiation and RAPD polymorphism of 90 Stipa grandis individuals from five populations were studied using RAPD markers . Sixteen oligonucleotide primers were used to amplify 310 RAPD loci , which were analyzed using several multivariate methods . The Principal Coordinated Analysis (PCoA) clearly clustered 90 Stipa grandis individuals into five groups in 3-dimension plot and the individuals from the same population were clustered into one group, even though the first three coordinates explained only 21.91% of the total variance. The Canonical Discriminant Analysis could
cluster individuals into their corresponding populations, with 97.8% of the correctness. The Spearman Rank Correlation and Multiple Regression Analysis established a strong and significant association between some of the RAPD loci and certain climatic factors ( annual precipitation, ≥10℃ cumulative temperature in a year, annual mean temperature, mean temperature in January and mean temperature in July). All these results indicated that (1) the genetic differentiation of Stipa grandis populations was significant, (2) the RAPD polymorphism was not randomly distributed but associated with the climatic characters of habitats, and (3) the natural selection of climatic divergence played an important role in affecting the genetic diversity and genetic structure of Stipa grandis populations. The results of this study may be useful for guiding the conservation of germplasm of Stipa grandis.

Key words: Stipa grandis