Genetic diversity and structure in populations of Elymus caninus (L.) L. (Poaceae)

Levels and distribution of genetic variation were assessed using allozymes in 54 populations of Elymus caninus from different locations in Denmark, Fi nland, Iceland, Italy, Norway, Sweden, Russia, China and Pakistan in order to obtain information on the extent and nature of genetic variation in this caespitose, predominantly self-fertilising, allotetraploid and perennial g rass species. Allozyme variation at the species level was high, with 71.4% of the loci being polymorphic, an average number of alleles per locus of 2. 2, and an average genetic diversity of 0.23. All 54 populations showed some level of polymorphism, which varied substantially from population to popul ation. A high degree of population differentiation was found, with the foll owing remarkable findings: (1) statistically significant differences were f ound in allele frequencies among populations for every polymorphic locus (P < 0.001), (2) 62% of the total allozyme Variation at polymorphic loci was partitioned among populations (G(ST) = 0.62), and (3) relatively high genet ic distances between the populations were obtained (mean D = 0.16). Genetic structuring was evident among populations from different geographical area s. The Nordic populations showed the highest levels of genetic variation. C luster and principal component analyses revealed the same genetic patterns of relationships among populations. Generally, this study indicates that E. caninus contains a high level of allozymic variation in its populations.