410107 Polygonum raii Bab.
- Bab., London Edinburgh Philos. Mag. & J. Sci. 8: 346 (1836). Described from the British Isles. - Polygonum oxyspermum subsp. raii (Bab.) D.A. Webb & Chater, Feddes Repert. Spec. Nov. Regni Veg. 68: 188 (1963).
2n=
(1) 40 (4x). - Europe (W), Canada. - At least five reports.
(2) 80 (8x). - Europe (British Isles). - Styles (1962).
Not included: A report of 2n = 60 (6x) from Iceland (Löve and Löve 1956a). The species is not accepted from Iceland and the report probably belongs to a taxon of the P. aviculare group.
Geography: Amphi-Atlantic.
Notes: Tzvelev: I prefer to treat Polygonum raii and P. norvegicum as two species.
Elven: They are parapatric taxa bordering on each other but not overlapping in southwestern Norway and western Denmark. Transitions are not documented but this may be due to the small contact zone or to the assumed predominant inbreeding. Rank as species may well be the best alternative but we follow Karlsson (2000c) and treat them as subspecies, also for the practical reason that the specific combination of P. norvegicum is illegitimate. Subspecies raii is amphi-Atlantic but non-arctic.