Kw. Hughes et al., Patterns of geographic speciation in the genus Flammulina based on sequences of the ribosomal ITS1-5.8S-ITS2 area, MYCOLOGIA, 91(6), 1999, pp. 978-986
Previous studies based on morphology and on ability to intercross suggested
that new biological and morphological species were sheltered within the ge
nus Flammulina as well as varieties within R velutipes. The currently descr
ibed or proposed Northern Hemisphere Flammulina species are F. "mexicana, "
F: populicola, E: rossica, F: ononidis, F: elastica, F: fennae and E veluti
pes. Within F. velutipes are E;: velutipes var. velutipes, var. "lupinicola
," and var, lactea. The ribosomal ITS1-5.8S-ITS2 region was sequenced for e
ighteen 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 Ij
: velutipes together with it's varieties, a clade consisting of E;: populic
ola and F: "mexicana" and clades representing F: fennae, R rossica and F. e
lastica together with F. ononidis. Data are consistent with the hypothesis
that F. populicola is a relatively old species which has diverged significa
ntly on different continents, possibly giving rise to F: "mexicana" in Nort
h America. The ITS sequence for Flammulina stratosa, an isolate from New Ze
aland, is highly divergent from all other Flammulina isolates and may repre
sent an ancient endemic or the product of very rapid evolution. Species div
ersity is highest in Europe and suggests that Europe may be a center of div
ersity for this group.