Patterns of geographic speciation in the genus Flammulina based on sequences of the ribosomal ITS1-5.8S-ITS2 area

Previous studies based on morphology and on ability to intercross suggested that new biological and morphological species were sheltered within the genus Flammulina as well as varieties within F. velutipes. The currently described or proposed Northern Hemisphere Flammulina species are F. "mexicana, "F. populicola, F. rossica, F. ononidis, F elastica, F. fennae and F. velutipes. Within F. velutipes are F. velutipes var. velutipes, var. "lupinicola," and var. lactea. The ribosomal ITS1-5.8S-ITS2 region was sequenced for eighteen geographically diverse Flammulina collections, including the three F. velutipes varieties. Results of neighbor-joining and parsimony analysis produced five distinct Northern Hemisphere clades, a clade consisting of F. velutipes together with it's varieties, a clade consisting of F. populicola and F. "mexicana", and clades representing F. fennae, F. rossica and F. elastica together with F. ononidis. Data are consistent with the hypothesis that F. populicola is a relatively old species which has diverged significantly on different continents, possibly giving rise to F. "mexicana"in North America. The ITS sequence for Flammulina stratosa, an isolate from New Zealand, is highly divergent from all other Flammulina isolates and may represent an ancient endemic or the product of very rapid evolution. Species diversity is highest in Europe and suggests that Europe may be a center of diversity for this group.