Five new species of North American Taraxacum (Asteraceae)
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Abstract. Five new species of native North American Taraxacum are described: T. argilliticola, T. cordilleranum, T. lautellum, T. pugioniferum, and T. simplex, all of them from high elevation habitats or high latitudes in western Canada, mostly from British Columbia. Keywords: British Columbia, North America, Taraxacum.
A workable taxonomy of temperate to boreal North American Taraxacum F.H. Wigg. (Asteraceae) has never been established, with species delimitation and identification being perceived as a near impossibility. Based on one or few morphological characters, most North Americans botanists apply a small number of Taraxacum names to a vast array of North American Taraxacum entities, inadvertently lumping together many undescribed species, and species that are not close relatives or even members of the same taxonomic section. This extremely broad taxonomic approach soon reveals its disadvantages when exploring North American Taraxacum both in the field and in the herbarium. A great number of North American species can be delimited that are well marked by morphological characters, are characterized in part by reproductive syndrome, and occupy distinct geographical ranges and ecological settings. In my view, study of North American Taraxacum has been hindered by several challenges, which have jointly contributed to the understudied nature of the genus in North America. Firstly, herbarium specimens of Taraxacum tend to be poor, typically represented by sparse material that is badly discoloured and poorly pressed and displayed. Secondly, the native North American members of the genus mostly grow in remote, poorly explored regions, especially in the far north, so herbarium specimens do not capture the full diversity that occurs on the continent.
Lastly, North American botanists have lacked a taxonomic framework that would allow them to recognize the diversity of North American Taraxacum, and potentially significant Taraxacum specimens to collect. Thus, the study of North American Taxaracum cannot be based solely on herbarium specimens, and I think previously published Taraxacum treatments should be used with extreme caution. As an example, previous North American treatments generally treat species having horned involucre bracts or species of small size as native, and those having no horns on the involucre bracts and a large size as exotic, a schema that I have found to be overly simplistic. In North America, there are numerous exotic species with horned bracts, and many exotic species are characteristically small, whereas many native species lack horns on the bracts and are of a large size. The confusion caused by North American Taraxacum treatments is apparent when reviewing herbarium collections, in which it is common to find the name T. officinale applied to a native species, or T. ceratophorum applied to almost any native no matter how dissimilar from that species. By contrast, European Taraxacum species diversity is well studied, and there botanists have available to them both a coarser taxonomy to delimit g
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