It is worth checking old data – validation of Asplenium onopteris L. presence in the most northeastern sites in Europe (Sudetes, SW Poland)

In Poland, isolated serpentine rocks are exclusive habitats of some Asplenium species, reaching here their north or northeastern border range. One of them was Asplenium onopteris, a diploid European species native to Mediterranean and Atlantic areas. Since the nineteenth century, Polish out-of-range sites of A. onopteris have been quoted in literature without critical verification. Thus, to verify occurrence of this species in Poland, we analyzed the nuclear DNA content and micromorphological features as well as critically reviewed the literature data. We proved that all individuals from Polish populations resembling A. onopteris were tetraploids and should be classified as A. adiantum-nigrum. In addition, we validated a taxon silesiacum reported as co-occurring with A. onopteris. The proposed diagnostic features are insufficient to indisputably delimit this taxon, and distinguishing it as a separate unit is not justified. Analyses of the DNA content revealed also the presence of a triploid A. ×centovallense, a new hybrid for Polish flora.