Plant genetic diversity and grazing management on the Qinghai-Tibetan Plateau: A case study of a dominant native wheatgrass (Elymus nutans)

• Higher genetic diversity was observed in three grazed areas and it decreased with the increase in grazing intensity.
• A low degree of genetic differentiation occurred among the populations under different grazing intensities.
• There was significant spatial structure with declining genetic ‘patch’ size at higher grazing intensities.
• Light grazing should be best applied on the high-cold Qinghai-Tibetan Plateau for the conservation of Elymu nutans.

Grazing management on the Qinghai-Tibetan Plateau in China concerns farmers, scientists and policy makers because of its geographical uniqueness. To investigate the effects of grazing on genetic diversity in native plants, the dominant perennial wheatgrass Elymus nutans was used as a model to examine genetic diversity and spatial population structure under different grazing intensities. Intra-population genetic diversity in three grazed areas was higher than un-grazed area; however, the genetic diversity decreased with increasing grazing intensity. Genotypes from four areas were separated into two groups (grazed and un-grazed) through a clustering analysis. Approximately 12% (Gst = 0.1487) of the DNA variation was apportioned among populations by AMOVA indicating a relatively low degree of inter-population genetic differentiation. Significant spatial auto-correlations and subpopulation structure were also observed within the four areas, and the genetic ‘patch’ size decreased with increasing grazing intensity. On the high and cold Qinghai-Tibetan Plateau, grazing is suitable for the maintenance of genetic diversity, and a light grazing intensity is optimal for the conservation of perennial grass germplasm and long-term grassland management.