The Population Genetic Characteristics Of Elymus Nutans Griseb.under Different Grazing Intensity

Grazing is the main use of natural pasture, and it has a great impact of grazing animals feed on plants and trampling on the growth of plants and spacies protection. Grazing behavior will have an impact on the grassland vegetation community composition, coverage of community, richness and structure and the grassland ecosystem. Recent studies have shown that, grazing is the main factor of grassland degradation, species decline and species diversity reduce, change of grassland ecological structure. In this study, we make different grazing intensity treatment on Elymus nutans Griseb., from the perspective of population genetics, molecular ecology, use ISSR markers to research the genetic diversity and genetic spatial structure of Elymus nutans Griseb.. In this experiment, chooses12ISSR primers, through research of genetic diversity and genetic spatial structure of Elymus nutans Griseb. with different grazing pressure to understand the changes of the genetic diversity, gene flow and space distribution, to reveals the molecular mechanism; From the perspective of conservation biology find the reasonable grazing intensity, and provide genetic evidence to the restoration of grassland vegetation and ecological protection for our country. The main results as follows:1、Grazing has significantly effect on Elymus nutans Griseb. population genetic diversity. With the increase of the grazing intensity, from light, middle to heavy, the population genetic diversity shows first increase, then decrease but is higher than the contrast treatment. Though this experiment, light graze conducives to maintain a high level of Elymus nutans Griseb. population genetic diversity.2、The grazing Elymus nutans Griseb. population and no grazing population have obviously distinguish. For grazing populations, light grazing treatment and moderate grazing treament have the highest similarity coefficient, followed is heavy grazing treatment.3、Detected in this study, among different grazing intensity treatments,Elymus nutans Griseb. populations have low genetic differentiation coefficient (Gst=0.1517, Nm=2.7951>1). Structure analysis showed that, among the populations detected significant gene flow, especially between light grazing treatment and moderate graing treatment. It proved once again that grazing promote the Elymus nutans Griseb. population gene flow.4、We detected the totale of135candidate ISSR loci to test which ISSR loci scored could be subject to selection under different grazing pressure. The result showed that14(10.4%) loci has been affected by grazing,3(2.2%) under very strong selection concluded that grazing has a certain degree of selectivity to individual loci.5、Natural grassland obviously has spatial autocorrelation, there are space genetic patches. Grazing has obviously influence on the genetic patch size of Elymus nutans Griseb.population, with increasing the grazing intensity, genetic plaques becoming smaller, especially heavy grazing has the biggest influence; the genetic patch size of not grazing, light, moderate and heavy respectively is20m,19m,18m and12m.These results indicate that, grazing can change the population genetic spatial structure; the greater the grazing intensity, the smaller the genetic spatch, the spatial structure within populations increasingly complex.