Reproduction and diversity of the endangered Salix lapponum L. populations in Eastern Poland

The main aim of the study was to increase the knowledge on the ecology and biology of the boreal relict Salix lapponum L., an endangered plant in Poland, in order to create an effective protection program. An important aspect was to determine the within- and among-population genetic diversity of the studied species in order to evaluate whether the basic stages of the generative reproduction cycle in the populations were correct. The results confirmed that S. lapponum pollen viability and germinability, for both fresh and stored pollen, were high and so were the seed germination ability and dynamics. All individuals were of sexual origin and the expected heterozygosity was moderate. In spite of this, young individuals were observed in only 1 out of 5 studied populations and it was the most numerous one. Although the genetic diversity among the populations was not very high (PhiPT = 0.12), it accumulated in a quite short period of time, probably during the second part of the 20th century, as a consequence of habitat fragmentation. A lack of gene flow, either by pollen or seeds, may lead to further differentiation of the populations and extinction of the smallest ones. For this reason, preventive measures should be undertaken in order to enlarge the existing populations and to reconstruct S. lapponum populations in selected sites where environmental conditions are the most similar to those preferred by this species.