Panarctic Flora

410202-03 The Bistorta officinalis aggregate B. elliptica, B. plumosa

Geography: Disjunct European - Asian - amphi-Beringian.

Notes: Elven, Murray, and Petrovsky: The Bistorta officinalis aggregate is disjunct alpine and arctic European, north-central Asian, and amphi-Beringian. The priority name, if considered as a single species, is B. officinalis Delarbre, Fl. Auvergne, ed. 2: 516 (1800), rather than B. major Gray, Nat. Arr. Brit. Pl. 2: 267 (1821), both nomina nova for Polygonum bistorta L., Sp. Pl.: 360 (1753) [Persicaria bistorta (L.) Samp., Herb. Port.: 41 (1913); lectotype (LINN): Herb. Linn. 510.3 (Jonsell and Jarvis 1994: 153)]. The European (and elsewhere cultivated) plants are known with two ploidy levels: 2n = 24 from southern Europe and northwestern Africa (at least three reports) and 2n = (44-)48-ca. 50 from Europe, Ukraine, and cultivated plants (numerous reports).

This is a very widespread group with a disjunct alpine and arctic pattern in Eurasia and parts of North America. The disjunctions in the temperate regions may have a late Tertiary origin, whereas the arctic ranges may be more recent. Like in several of these groups, the first species name in the B. officinalis aggregate is based on plants in the temperate European part. Linnaeus (1753) described Polygonum bistorta "in montibus Helvetiæ, Austriæ, Galliæ", and the type should be from western or central Europe. All northern and arctic plants differ appreciably from the southern montane/alpine ones - in Europe, Asia, and western North America - and should be treated as one or more taxa apart from the temperate ones. There are several proposals for treatment. Petrovsky (1966) accepted one species, assigned the arctic plants from northeastern European Russia to Taimyr in northern Siberia to Polygonum bistorta subsp. bistorta (= Bistorta officinalis) and those from Anabar-Olenyok in northeastern Siberia to the Chukchi Peninsula to subsp. ellipticum. We follow his division but not his application of names. Tzvelev (in comment) considered the reports of subsp. officinalis (= subsp. bistorta, = subsp. major) from the Arctic probably to be erroneous, that both European and Siberian arctic plants are referable to subsp. elliptica, and that a treatment as species might be appropriate. We largely support that proposal.

Both Petrovsky (1966) and Hultén (1968a) considered northern Asian "elliptica" and North American "plumosa" to be one taxon. For a species, the name Polygonum ellipticum 1825 has priority before Polygonum plumosum 1901, for a subspecies subsp. plumosa 1944 before subsp. elliptica 1966. The assignment of all northern Asian and North American plants to a single entity is, however, problematic. Elven and Murray studied some herbarium material (ALA, O) from the whole arctic range and also some non-arctic material, supported by field observations in Yakutia, Chukotka, Alaska, and the Yukon Territory. They reached the following conclusions:

(a) Temperate European B. officinalis s. str. differs in several features from all the northern plants. We have not observed any transitions. Treatment of B. officinalis as a species apart from the northern plants seems the most appropriate.

(b) The northern plants are less different from each other and could be treated as one species with two races. However, the plants of northeastern Europe and northwestern and south-central Siberia (subsp. bistorta in Petrovsky's nomenclature) differ in several features from those of northeastern Siberia and the Russian Far East (subsp. elliptica in Petrovsky's nomenclature). The characters presented in the key in Flora Arctica URSS are applicable. We support Petrovsky's conclusion that these should be treated as two different taxa but we apply the names different from Petrovsky (1966).

(c) Like Petrovsky (1966) and Hultén (1968a), we find very little (if any) morphological difference between the northeastern Asian plants named subsp. elliptica by Petrovsky and the northwestern North American ones named subsp. plumosa. They may differ in ploidy levels. Russian plants are counted with 2n = ca. 46-50, northwestern North American ones with 2n = ca. 72, but the number of counts from North America is very small and this difference may not be consistent. We prefer to connect the northeastern Asian and the northwestern North American plants within one taxon, i.e., giving weight to morphology.

(d) This is a disjunct montane-alpine complex of taxa with a connection through the Arctic in northern Russia-Siberia and Beringia. The taxa could be treated either as three species, as two species, one with two races, or as three major geographical races. We consider them as three species, two as reaching the Arctic and both different from B. officinalis. We accept B. elliptica in northeastern Europe and northwestern Siberia (for the proposed shift of this name from one species to the other, see below), whereas a morphologically uniform but chromosomally perhaps variable B. plumosa is present in northeastern Asia and northwestern North America. Also Freeman and Hinds (2005) accepted the northwestern North American and northeastern Asian plant as B. plumosa.