Genetic structure of remnant black poplar (Populus nigra L.) populations along biggest rivers in Serbia assessed by SSR markers

Black poplar (Populus nigra L.) is a keystone species of riparian softwood forests along riversides in vast areas of Europe, Western Asia and Northern Africa. Since the end of the 20^th century, black poplar has been recognized as an endangered species throughout Europe due to the loss of its natural habitat and possible crossbreeding with hybrid poplars. Using twelve nuclear SSR loci, we analysed the genetic structure of four native populations from three river valleys in the northern part of Serbia. All tested loci were highly polymorphic, displaying 8 to 25 alleles per locus, overall 179 detected alleles and an average effective number of alleles 5.87. Observed heterozygosity (overall Ho = 0.703) has been lower than the expected (overall H_e = 0.808) in each population, which indicates positive mean of fixation index values (overall F_is > 0 (0.132)). An AMOVA analysis revealed that the highest degree of genetic variation occurred within populations (95.33 %) while the genetic variation between populations was really low (4.67 %). High gene flow and no significant loss of allelic diversity have been recorded in the studied populations in Serbia.