In a recent paper on the genus Lepraria (Lendemer & Hodkinson 2013), my co-author and I established a new genus named 'Nelsenium' for Lepraria usnica, a corticolous, Paleotropical species (Sipman 2003) that had previously been misclassified. The name honors Matt Nelsen, a fellow North American lichenologist who was the first to sequence Lepraria usnica and conducted molecular phylogenetic analyses to determine its familial affinities within the Lecanoromycetes. When Nelsen et al. (2008) used mtSSU sequence data to infer the higher level systematic placement of Lepraria usnica, they recovered the species as a member of the Pilocarpaceae (which is not the family of Lepraria). In our recent paper we affirmed this based on an analysis of 11 mtSSU sequences of Pilocarpaceae including L. usnica. Nelsen et al., however, did not formally describe a new genus to accommodate this species, so we established the genus Nelsenium to place L. usnica in its proper context.
We used a molecular diagnosis for this genus, naming the particular nucleotide positions that were unique in the mtSSU region.
"Diagnosis: A genus of the Pilocarpaceae, with a sterile, leprose crustose thallus whose mtSSU sequence (AY300894) differs from those of Fellhanera bouteillei (AY567787) and F. subtilis (AY567786) at these nucleotide sites: adenine at positions 96, 106, 232, 355, 689, 760, 806 and 813; cystine at positions 146 and 741; guanine at positions 44, 101 and 292; and thymine at positions 83, 233, 254 and 909."
I think this type of approach will become more and more common, especially in fungal taxonomy, where synapomorphies are often very difficult to find (especially for higher-level taxa) if one does not resort to examining the primary structure of nucleic acids or proteins.
To see how the new genus looks, feel free to peruse these photos of the type specimen of the type species, Nelsenium usnicum (Sipman) Lendemer & Hodkinson:
Lendemer, J.C., and B.P. Hodkinson. 2013. A radical shift in the taxonomy of Lepraria s.l.: molecular and morphological studies shed new light on the evolution of asexuality and lichen growth form diversification. Mycologia 105: 994-1018.
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Nelsen, M.P., H.T. Lumbsch, R. Lucking, and J.A. Elix. 2008. Further evidence for the polyphyly of Lepraria (Lecanorales: Stereocaulaceae). Nova Hedwigia 87: 361-371.
Sipman, H.J.M. 2003. New species of Cryptothecia, Lepraria, and Ocellularia (lichenized Ascomycetes) from Singapore. Bibliotheca Lichenologica 86: 177-184.