Clonal structure of field elm (Ulmus minor Mill.) in Poland

Field elm (Ulmus minor Mill.) is distributed mainly across central and southern Europe. In Poland this species occurs in the lowlands and foothills, where it grows mainly in the floodplain forests along the rivers. U. minor exists in a variety of climatic and ecological conditions. It is capable to tolerate floods as well as drought. Currently, most populations of U minor are small and fragmented resulting from human activity and Dutch elm disease. Moreover, in the natural field elm populations, vegetative propagation by root suckers or sprouting can be observed. All these factors may affect the level of genetic variation of U. minor populations in Poland. In the present study, we determined the level of genetic variation and the clonal diversity of twelve natural U. minor populations in Poland (407 individuals) using eight nuclear microsatellite loci. The obtained results indicate that the studied field elm populations are characterized by low level of genetic variation (H-e =0.382; H-o =0.555; A=7.0). Additionally, the high level of clonality in field elm populations was estimated. The clonality level of examined elm populations varied among them, and in some cases was very high. Out of the 407 individuals analysed for clonal structure only 61 multilocus genotypes were identified. Furthermore, only one genotype was identified in the three study populations of field elm, which means that in each of these populations all trees belong to one genet. The values of genotypic richness (R) were heterogeneous among populations, with mean 0.148. The knowledge on the genetic diversity and the clonal structure of U. minor populations is essential to make future decisions regarding conservation of genetic resources of this species in Poland.