Abstract
In Poland, isolated serpentine rocks are exclusive habitats of some <em>Asplenium</em> species, reaching here their north or northeastern border range. One of them was <em>Asplenium onopteris</em>, a diploid European species native to Mediterranean and Atlantic areas. Since the nineteenth century, Polish out-of-range sites of <em>A. onopteris</em> 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 <em>A. onopteris</em> were tetraploids and should be classified as <em>A. adiantum-nigrum</em>. In addition, we validated a taxon <em>silesiacum</em> reported as co-occurring with <em>A. onopteris</em>. 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 <em>A. ×centovallense</em>, a new hybrid for Polish flora.
Highlights
The European Asplenium adiantum-nigrum complex includes three related and morphologically variable taxa: diploid A. cuneifolium Viv. and A. onopteris L. and their stable tetraploid hybrid A. adiantum-nigrum L. [1]
The presence of Asplenium onopteris in the Sudetes refers mainly to one population from a serpentine rock outcrop in the Gozdnik Hill discovered and recorded by Milde as A. silesiacum [14,19]. This name was maintained during the subsequent division of the A. adiantum-nigrum group into three species [19]: (i) A. adiantum-nigrum with five varieties, (ii) A. serpentini Tausch with four forms, and (iii) A. silesiacum Milde, for which A. adiantum-nigrum subsp. silesiacum was given as a synonym
Lower Silesia was a province of Prussia but A. onopteris was not included in the flora of Germany [26,27] until 1903, when it was mentioned as A. adiantum-nigrum subsp. onopteris Heufl. with var. silesiacum Milde [28]
Summary
The European Asplenium adiantum-nigrum complex includes three related and morphologically variable taxa: diploid A. cuneifolium Viv. and A. onopteris L. and their stable tetraploid hybrid A. adiantum-nigrum L. [1]. Asplenium cuneifolium is associated with serpentine rocks in Southern Europe, up to southern Germany and southwestern Poland [2]. The most frost-resistant, circumpolar, and cosmopolitan A. adiantum-nigrum can colonize other types of rock [3]; its European range covers the Atlantic and subMediterranean area up to western Norway, southwestern Poland, Slovakia, Ukraine, and Romania [4]. In Poland, all species of the complex with the only Central European population of A. onopteris and the locus classicus of A. silesiacum Milde are associated exclusively with serpentine rock outcrops in the Sudetes. The latter taxon is currently included in A. adiantum-nigrum though
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