The delimitation of Flammulina fennae
Multivariate morphometric analyses of micromorphological characters measured on 35 specimens of Flammulina fennae and related species show that only a combination of spore dimensions and ixohyphidia characters are suitable for delimitation
of this species. In order to confirm species identifications based on micromorphology, ribosomal ITS DNA sequences were obtained
and compared with those previously deposited in GenBank, and phylogenetic analyses were performed using an ITS dataset of
all known Flammulina species. All six specimens morphologically determined as F. fennae were identified by molecular data. Two of twelve specimens morphologically assigned to F. velutipes had F. elastica sequences. One ITS sequence of F. velutipes appears to be a hybrid: the ITS1 region is homologous to F. velutipes and ITS2 is homologous to another Flammulina species, F. rossica. Variability of morphocharacters observed for F. fennae and related species is discussed and compared with the data from previous studies. A key is provided to European taxa of
the genus Flammulina together with a full description of F. fennae.