Levels and distribution of allozyme and RAPD variation in populations of Elymus fibrosus (Schrenk) Tzvel. (Poaceae)

Abstract

To study the magnitude and nature of genetic variation in E. fibrosus, the levels and distribution of allozyme and RAPD variations were investigated in populations collected from Finland and Russia. The results obtained from the allozyme and RAPD studies were compared to each other in 10 of the populations. The allozyme analysis showed that 6 of 12 presumed loci (50%) were polymorphic within the species, while the mean number of polymorphic loci within populations was 4.8%. The mean number of allele per locus for the species was 1.5 and 1.05 across the populations. Genetic diversity at the species level was low (Hes = 0.025), and the mean population genetic diversity was even lower (Hep = 0.007). Both these values were much lower than the average for other Elymus and self-fertilising species. The largest proportion of the total allozyme diversity was found among, rather than within the populations (GST = 0.70). The allozyme genetic distances between the populations did not reflect geographic distances. Cluster and principal coordinates analyses revealed the same allozyme relationship patterns among the populations. A comparison of allozyme and RAPD variation in 10 of the populations showed differences in the amount of genetic variation. The RAPD analysis revealed higher levels of variation (Ap = 1.19, Pp = 20.3 and Hep = 0.09) than the allozyme one) Ap = 1.06, Pp = 5.8 and Hep = 0.008). For both markers, the largest proportion of the total gene diversity was found among the populations studied (Gst = 0.63 for RAPDs and Gst = 0.65 for allozyme). In contrast to the allozyme analysis, the RAPD based genetic distances did reflect geographic distances. The cluster and principal coordinates analyses showed different grouping of populations for each data set. There was a positive, but not significant, correlation (r = 0.41) between the genetic distance matrices resulting from these markers. Regional comparison revealed that the Finnish populations had a higher diversity than the Russian ones. Generally, this study indicates that E. fibrosus contains low genetic variation in its populations. The results are discussed in the context of conservation of the species.