Reviewing the identity of the Maltese Polypodium(Polypodiaceae) – new evidence from morphology and flow cytometry

The first record ofPolypodiumfrom Gozo (Maltese Islands) was described as a new endemic taxon,Polypodium vulgaresubsp.melitense, based on its unique set of morphological characters. It was treated as a novelty and designated as a subspecies ofP. vulgaremainly due to the lack of paraphyses, the presence of 10–16 annular cells, and a mean spore length of 64 μm. The fern was reassessed by us employing a more rigid morphological analysis and the application of flow cytometry. The absence of paraphyses was confirmed, but the number of annular cells (5–11) and the spore length (70–79 μm) differed from the previous study. These and other morphological traits, the phenology (leaf-shedding in spring), the calcareous growth habitat, and the southern distribution implied that the fern isP. cambricum.Final confirmation was obtained from flow cytometry; the genome size of 17 pg corresponds perfectly with the range obtained for other accessions of this diploid species. ThePolypodium reported from Malta does not merit taxonomic distinction despite being a rare form ofP. cambricum, which lacks paraphyses.