Effects of heavy grazing pressure on the random amplified polymorphic DNA marker diversity of mountain rough fescue (Festuca campestris Rydb.) in south western Alberta

The Fescue Grassland is found in the western portion of the Northern Great Plains in Canada. Grazing and cultivation threaten this grassland, and a better understanding of its character is needed to preserve its integrity. Mountain rough fescue is highly sensitive to grazing during the growing season, which results in smaller plants and the death of some. The death of plants suggests the potential loss of genetic diversity. Therefore, we compared the genetic diversity of mountain rough fescue plants from sites in south western Alberta (50°12′N, 113°54′W) that had either been heavily grazed by livestock or left ungrazed for 52 yr to determine if grazing pressure had affected their genetic composition. Thirty-four and 43 plants were sampled in the spring of 2001 from very heavily grazed and ungrazed subpopulations, respectively, and their DNA was analyzed using random amplified polymorphic DNA (RAPD). Of the 15 primers used, 12 generated an average of seven polymorphic loci each. Ten loci were present at a frequency of 0.10 or less in the heavily grazed subpopulation and six in the ungrazed subpopulation. RAPD marker diversity between the heavily grazed and ungrazed subpopulations of mountain rough fescue was mainly the result of frequency differences (P < 0.05) produced by 20% of the total markers that were examined, while the subpopulations accounted for only 4.37% of total heterozygosity. Therefore, grazing affected frequency of some markers but did not eliminate genes that may be linked with grazing sensitivity or tolerance. Lack of clear genetic segregation between the subpopulations might be caused by a high gene flow (Nm = 10.92). This mechanism requires further testing in order to prescribe a suitable management response for restoring overgrazed grasslands. Key words: RAPD frequency, F-statistics, genetic identity, genetic distance, gene flow