3418 Vahlodea Fr.
- Fr., Bot. Not. 1842: 141, 178 (1842).
Notes: Vahlodea is disjunctly distributed in three well separated areas: northern amphi-Atlantic regions, northern amphi-Pacific regions, and southernmost South America. From one (V. atropurpurea) to four species or races have been proposed. Tzvelev (in comment) proposed, besides the South American V. magellanica (Hook. f.) Tzvelev, three northern species. The amphi-Atlantic V. atropurpurea s. str. is allopatric from the Pacific plants and differs morphologically from these, in our opinion perhaps most from the North American V. latifolia. The most evident difference reported between the mainly northeastern Asian V. paramushirensis and the northwestern North American V. latifolia is that the Asian plants have pubescent leaves, whereas the majority of North American plants have glabrous leaves. They differ in general habit, e.g., when plants from western Canada are compared with plants from Japan or Kamtchatka, but there are many transitions, especially in south-central Alaska. Soreng et al. (2003) recognized one species with two subspecies: subsp. atropurpurea (including both V. latifolia and V. magellanica) and subsp. paramushirensis. Cayouette and Darbyshire (2007c) recognized one species without races and without comments on the variation.
The solution we have chosen is to recognize two northern species, one amphi-Atlantic and one amphi-Pacific, the latter with two intergrading subspecies. Alternative solutions are three subspecies of one species, or three species, in which case the priority name for the Asian taxon is V. flexuosa (Honda) Ohwi.