The genetic assessment of the natural regeneration capacities of black poplar populations in the modern river valley landscapes

Abstract

Black poplar (Populus nigra L.) is an economically and ecologically important tree species which in the past was widely distributed along riversides in vast areas of Europe. Currently, it deserves conservation with a view of serious threats resulting from the species habitat reduction and progressive introgressive hybridization. Here we examined the regeneration capacities of black poplar populations from the Vistula River in Poland in a region which has been influenced by man-made disturbance regimes. Using both nuclear (nDNA) and chloroplast (cpDNA) genetic markers and spatial location data we: (1) evaluated the susceptibility of the studied populations to introgression, (2) determined genetic diversity of the analyzed offspring and compared it with their maternal stands, and (3) assessed the level of gene flow among populations and generations. Nine hybrid individuals were identified in the examined groups of one-year poplar seedlings. Both molecular variance and clustering analyses showed that the gene pool of black poplar populations was homogenous (FST = 0.004, p = 0.623). Heterozygosity and allelic richness were comparable between adult and their progeny populations, and there were also no strong disturbances in a random distribution of genotypes in the study area. Low spatial genetic structure was observed in two seedling groups and among all black poplar individuals from the Wysoczyn population. The results are discussed in the context of natural regeneration capacities of the remaining black poplar populations and protection of the species genetic resources along the landscapes of the river valleys.