DNA ploidy in <i>Salix retusa</i> agg. only partly in line with its morphology and taxonomy

4 June 2019

Kosiński, Piotr; Sliwinska, Elwira; Hilpold, Andreas; Boratynski, Adam

Salix retusa agg. encompasses small, prostrate willows occurring in the subalpine and alpine zones of European mountains. Karyological relationships among taxa in this group remain unclear. DNA ploidy was estimated using flow cytometry of silica-dried specimens, covering the entire distribution area of the species. In this study, the presence of two main lineages was revealed: exclusively diploid S. serpyllifolia and predominantly octoploid S. retusa s.l. Only in the western and eastern limits of the distributional range of the latter species different levels of DNA ploidy occurred: hexaploidy in the Western Pyrenees, and up to decaploidy in the Southern Carpathians. In the Western Pyrenean populations, the lower ploidy corresponded to smaller leaf sizes as compared to other populations of S. retusa s.l. The elevated ploidy in the Southern Carpathian populations did not translate into bigger dimensions of plants in this area. However, the populations from the northern part of the Carpathian arc, distinguished by larger leaves and sometimes considered as a distinct taxon (S. kitaibeliana), consisted mainly of octoploid individuals. Thus, DNA ploidy estimations did not confirm the separate taxonomic status of S. kitaibeliana.