The Taxonomic Circumscription and Nomenclatural History of Pilosella suecica (Asteraceae): A Special Case of Grey Literature in Taxonomic Botany

The taxonomic history, nomenclature and application of the oldest species names available for the common hybrids between Pilosella caespitosa and P. lactucella are reviewed. Elias Fries created a nomenclatural and bibliographical collision when he replaced a printed label of his exsiccata Herbarium normale with its second version, distributed at a later date, in which the protologue of Hieracium suecicum had appeared. In this protologue, the new species name was validly published with a mere reference to the original description of H. auricula var. majus, thus being based on the type of the latter. In a later fascicle of the same exsiccata, Fries excluded this synonym and distributed a different morphotype of H. suecicum, which caused taxonomic confusion and re-description of the same taxon under the name H. fennicum. The surviving original material of H. auricula var. majus is rejected, and its neotype is designated, making H. suecicum the correct name for the hybrids strictly intermediate between P. lactucella and P. caespitosa. Such hybrids constitute the most common hybridogenous taxon of Pilosella in Scandinavia, Finland and neighbouring Russia, with many synonyms described from this area and partly typified here. Another hybridogenous taxon of the same origin, more similar to P. lactucella and previously known as P. cochlearis, is correctly named P. stipitiflora comb. nov. The nomenclatural value and bibliographic complexity of exsiccata, a commonly underestimated kind of grey literature in taxonomic botany, are further highlighted.