Preissia quadrata (Scop.) Nees (Marchantiopsida, Marchantiaceae) is a northern hemisphere species usually defined as having two geographically distinct subspecies: Preissia quadrata (Scop.) Nees ssp. quadrata and P. quadrata ssp. hyperborea R.M. Schust. The subspecies quadrata is considered to have a temperate-boreal distribution, whereas the subspecies hyperborea is probably restricted to Arctic / Sub-Arctic / alpine regions. Until recently, the subspecies hyperborea had been documented from only a few jurisdictions in North America. This article describes new records of the subspecies hyperborea in Canada, including the first reports for Alberta based on field collections, and for Labrador, Northwest Territories, and the Yukon based on annotations of herbarium collections of Preissia quadrata that belong to the subspecies hyperborea. An updated distribution map of the subspecies hyperborea in North America is provided. The subspecies hyperborea is shown to be more widely distributed in northern and montane regions of the continent than previously reported; however, some taxonomic impediments remain for the Preissia quadrata complex. An improved understanding of the phenology of the subspecies hyperborea across its range may facilitate its circumscription.
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Vol. 33 • No. 2