ISSN 1188-603X

No. 390 March 12, 2008 Victoria, B.C.
Dr. A. Ceska, P.O.Box 8546, Victoria, B.C. Canada V8W 3S2


From: Reidar Elven (Oslo) and David F. Murray (Fairbanks)

[This article is based on the authors’s treatment of Potentilla for the Flora of North America project. The authors will gratefully acknowledge your comments.]

While reviewing arctic and boreal Potentilla for our contribution to the forthcoming treatment of the entire genus in Flora North America, we determined that some of the highly variable species can be divided into taxa to which Asiatic names may be applied. Potentilla uniflora group is one of these variable species.

The name Potentilla uniflora Ledeb. and its superfluous replacement name P. ledebouriana A.E.Porsild, has been applied extensively to compact, tufted plants of exposed ridges and mountain tops in northwestern North America with a single, large, showy flower or few-flowered inflorescences. This species is distinct from the Pacific coastal P. villosa Pallas ex Pursh and also from the high arctic P. vahliana Lehmann described from Greenland.

Our late friend and colleague Boris Yurtsev (Yurtsev 1984, 1993, 2001) and Ji?í Soják, the contemporary student of Potentilla (Soják 2004) have in recent decades accepted several more species in this complex, and their work has influenced our review and shaped our results. We focused on three questions: 1) how many entities (species) should be recognized in northwestern North America? 2) how are they characterized? and 3) what names should be applied?

That hybridization produces more or less agamospermic hybrid species is a well documented feature of several sections of Potentilla (e.g., Gustafsson 1947a, 1947b; Asker 1977; summary by Asker & Jerling 1992), not the least sect. Niveae to which the P. villosa-uniflora group belongs (cf. Eriksen 1996, 1997). Diploids (2n = 14) and most tetraploids (2n = 28) reproduce sexually, whereas plants at higher ploidy levels are reported to reproduce by agamic seeds, often in combination with some sexuality. A few studies suggest that the reproductive model established for more temperate species is relevant here (Yurtsev 1984; Soják 1985, 1986).

The names relevant to the Potentilla villosa-uniflora group and the species split from P. uniflora by Russian/European authors for northeastern Asia and northwestern North America are examined below with their chromosome numbers and ranges.

Potentilla villosa Pall. ex Pursh, Fl. Amer. Sept. 1: 353. 1813. – Described from Alaska: "northwest coast of North America". – Reported from northwestern North America from Washington north to southern and southwestern Alaska and from Russian Commander Islands. – Diploid (2n = 14) in several counts from North America.

Potentilla villosula Jurtz., Fl. Arct. URSS 9(1): 319, 191. 1984. – Type: Russian Far East: east Chukotka, Chukchi Peninsula, "sinus Emma", 13.07.1938, leg. B.N. Gorodkov (LE) holotype. – Reported from a large area in Alaska and Yukon Terr. and from the Russian Far East, mainly the Chukchi Peninsula. – Tetraploid (2n = 28) in several counts from Chukotka.

Potentilla uniflora Ledeb., Mém. Acad. Imp. Sci. St. Pétersbourg Hist. Acad. 5: 543. 1815. – Described from Russian Far East: E Chukotka, per protologue "terra Tschuktschorum ad sin. St. Lawrentii", leg. Eschscholz. However, the plants from “terra Tschuktschorum ad sin. St. Lawrentii” are not P. uniflora as currently understood. The type material is heterogeneous, possibly with plants from other regions and thus typification remains uncertain. – P. ledebouriana A.E.Porsild, Bull. Natl. Mus. Canada 121: 226. 1951. A superfluous replacement name for P. uniflora. – Reported as widespread in northern and northeastern Asia from Taimyr Peninsula eastwards to the isthmus of the Chukchi Peninsula, but not from the peninsula itself (except for the “type locality”). Whereas both Yurtsev and Soják have annotated plants from Alaska and Yukon Territory (ALA) as P. uniflora, these sheets can be placed into other taxa following the diagnostic characters given by them` – Tetraploid (2n = 28) in numerous counts from Chukotka and hexaploid (2n = 42) in several counts from northern Yakutia and Chukotka. There are also tetraploid counts under this name from Yukon Territory (Mulligan & Porsild 1969, 1970) and from Alberta (Packer & Whitkus 1982), but the vouchers for these counts must be re-examined. If we are correct that P. uniflora is absent from North America, these counts must be reassigned to other species.

Potentilla vulcanicola Juz., Bot. Mater. Gerb. Bot. Inst. Komarova Akad. Nauk SSSR 17: 222. 1955. – Type: Russian Far East: Kamtchatka, Petropavlovsk area, 09.07.1930, leg. I. Zhirov & E. Sokovnina (LE) holotype. – Reported from northern parts of the Russian Far East and from Alaska, Yukon Territory, Northwest Territories, and western Nunavut. – Tetraploid (2n = 28) from southern Chukotka.

Potentilla subvahliana Jurtz., Fl. Arct. URSS 9(1): 319, 194. 1984. – Type: Russian Far East: Wrangel Island, "in curso medio fl. Gusinaja, ad rivulum Leningradskij", 02.07.1970, leg. P.G. Zhukova & V.V. Petrovsky (LE) holotype. – Reported from northern parts of Russian Far East, Alaska, Yukon Territory, and all the arctic parts of Northwest Territory and Nunavut. – Tetraploid (2n = 28) in numerous counts from Chukotka.

Potentilla gorodkovii Jurtz., Fl. Arct. URSS 9(1): 319, 190. 1984. – Type: Russian Far East: Wrangel Island, "in cursu medio fl. Gusinaja, ad rivulum Leningradskij", 21.07.1970, leg. P.G. Zhukova & V.V. Petrovsky 70-161 (2n = 28) (LE) holotype. – Reported from northern parts of Russian Far East. – Ten counts from Wrangel Island, tetraploid 2n = 28 (2 counts), hexaploid 42 (1), septaploid 49 (2), and octoploid 56 (5).

Potentilla subgorodkovii Jurtz., Bot. Zhurn. (Moscow & Leningrad) 78(11): 83. 1993. – Type: Northern Alaska: Sheenjek River north of junction with Old Woman Creek, 22.06.1956, leg. B. Kessel (ALA) holotype. – Reported from Alaska, Yukon Territory, and from northern Russian Far East. – No chromosome counts have been reported.

Studying these taxa and applying the criteria proposed by Soják and Yurtsev, we could assign most of the specimens to five of these seven species. We concluded that these five taxa are morphologically coherent and separable from each other. Two features need some explanation.

The genus Potentilla is rich in hairs of different types, and these hair types are diagnostic. Understanding them is critical to following our taxonomy. The main types in sect. Niveae are long straight and stiff hairs (mostly 1–2 mm) which are verrucose (50x magnification) or more rarely smooth; long ± straight, soft hairs (same lengths), which are smooth or more rarely verrucose; short stiff hairs (mostly < 0.5 mm); short crisped hairs (mostly < 0.5 mm); and floccose hairs which are flat (50x magnification) and appear as crinkly, often in a dense tomentum. In addition, there can be stipitate glands. These hairs appear in different proportions on different parts of the plants. In the P. villosa-uniflora group, the diagnostic features are mainly found in the hairs of the petioles, to a lesser degree on the abaxial and adaxial leaf surfaces.

The achenes are embedded on a hairy receptacle. These hairs should not be confused with the diagnostically significant hairs that can occur apically on achenes. Such hairs are, according to Yurtsev (1984), a rare feature in Potentilla, mainly found in assumedly "primitive" sections, but present in at least two entities of the P. uniflora group.

Key to northeastern Asian and northwestern North American representatives

The following key is based on Yurtsev (1984) and Soják (2004) but includes some additional features and excludes characters we have found unreliable.

1.    Petioles with a combination of floccose hairs and ascending to
      spreading long, straight, smooth hairs and often with crisped hairs

      2.    Caudex branches covered with remains of stipules and petioles
            but not entire leaves      P. gorodkovii

      2.    Caudex branches covered with remains of entire leaves
                    P. subgorodkovii

1.    Petioles without floccose hairs, covered by ascending to spreading
      long, smooth straight hairs, often with shorter crisped hairs

      3.    Achenes hairy at apex

            4.    Leaflets sparsely hairy adaxially; abaxial veins not densely
                  hairy with straight hairs; epicalyx bractlets lanceolate–oblong;
                  achenes with numerous apical hairs. . .        P. vulcanicola

            4.    Leaflets densely hairy, often sericeous adaxially; abaxial veins
                  densely hairy with straight hairs; epicalyx bractlets elliptic;
                  achenes with a few hairs apically P. villosula

      3.    Achenes glabrous at apex

            5.    Epicalyx bractlets broad, ovate or elliptic; inflorescences many-
                  flowered (3–7); leaflets with ca. 4–6 teeth per side, teeth rounded 
                  with reflexed margins    P. villosa

            5.    Epicalyx bractlets narrow, oblong or lanceolate; inflorescences few-
                  flowered (1–3); leaflets with ca. 2–3 teeth per side, teeth subacute
                  to acute with scarcely reflexed margins

                  6.    Caudex branches covered with remains of stipules and petioles, 
                        without entire leaves

                        7.    Leaflets sparsely hairy adaxially; inflorescences mostly 
                              1-flowered    P. uniflora

                        7.    Leaflets densely sericeous adaxially; inflorescences 
                              mostly 2–3(–4)-flowered    P. villosula

                  6.    Caudex branches covered with remains of entire leaves

                        8.    Leaflets sparsely hairy adaxially; inflorescences mostly 
                              1-flowered    P. subvahliana

                        8.    Leaflets densely sericeous adaxially; inflorescences 
                              mostly 2–3(–4)-flowered               P. villosula

Relationships, variation and ranges

Yurtsev (1984) and Soják (2004) considered some species primary and others hybrid species. Potentilla gorodkovii and P. subgorodkovii are considered hybrid species because they combine the floccose hairs of Potentilla nivea s. lat. and the long, straight hairs of P. uniflora s. lat., are many-flowered and have more numerous teeth on the leaflets than P. uniflora s. lat. They postulated P. gorodkovii from P. nivea L. x P. uniflora and P. subgorodkovii from P. crebridens Juz. x P. subvahliana. Potentilla villosula is considered by both authors a hybrid species, by Soják (2004) as originating from P. villosa x P. uniflora or P. vulcanicola. They consider P. subvahliana, P. uniflora, P. villosa, and P. vulcanicola primary, i.e., not originating from hybridization.

To a large degree, we share these views. Potentilla villosula combines characters otherwise found only in P. villosa and P. vulcanicola and is, in addition, more polymorphic than its assumed parents. This may be because of repeated hybridizations. Potentilla subgorodkovii always combines features of P. nivea s. lat. and P. uniflora s. lat., but we are very reluctant to accept that all plants in northwestern North America that combine these features originate from the cross P. crebridens (nivea group) x P. subvahliana (uniflora group), as proposed by Yurtsev (1993).

Instead we see a consistent, albeit polymorphic, group of plants that share characters probably from both P. crebridens and P. nivea on one side and from P. subvahliana, P. villosula, and P. vulcanicola on the other side. These influences are very difficult to separate without molecular analysis, and no such investigation has been undertaken. Until the variation pattern is resolved we prefer to accept one northwestern North American hybrid species from P. nivea s. lat. x P. uniflora s. lat., and to apply the Alaskan name P. subgorodkovii.

Two of the species have not been confirmed for northwestern North America. Potentilla uniflora has been determined on Alaskan material several times by Yurtsev and Soják, but we have redetermined all these specimens as other taxa. The nearest confirmed sites of P. uniflora are at the isthmus of Chukchi Peninsula. Given the uncertain typification of the name, we base our concept of P. uniflora on current usage in Russia. The species in that sense is absent from North America.

The northeastern North American and Greenlandic Potentilla vahliana belongs in the same relationship, presumably as a hybrid species from P. nivea s. str. x P. subvahliana. Both of these cross-group hybrid species are much closer morphologically to their presumed P. uniflora parents than to their P. nivea parents, and they are fairly easily distinguished from the presumed primary hybrids that often are observed. This morphological pattern suggests some back-crossing with a parent from the P. uniflora group before stabilization of the hybrid species.

The ranges of the five species present in northwestern North America are slightly different but with a huge area of overlapping ranges in Alaska, Yukon Territory and western parts of Northwest Territories. The ecological differences are not very pronounced, except for the coastal Potentilla villosa, and among the other species co-occurrences have resulted in numerous mixed collections.

Potentilla villosa is distinctly coastal with very few records above 50 msm, and it is apparently without a preference for base-rich substrates. The southernmost occurrences are in northwestern Washington, the northernmost in western Alaska south of Seward Peninsula. It is much more restricted in the north than mapped by Hultén (1968).

Potentilla villosula is coastal, alpine and arctic. Whereas P. villosa shows preference for coastal cliffs, P. villosula shows preference for sandy shores and sand dunes (where it can be a spectacularly subdominant species), but also for alpine and southern arctic tundra fellfield on circumneutral and base-rich sites.

Populations of Potentilla villosula close to the range of P. villosa are more similar to that species than those farther away, and the distant populations have the columnar caudex found within the more northern range of P. subvahliana. In North America P. villosula is restricted to Alaska, western parts of Yukon Territory, and northernmost British Columbia. The major part of the range mapped by Hultén (1968) for P. villosa belongs to P. villosula, whereas a smaller part of the range mapped by Cody (1996, 2000) for P. villosula belongs to that species.

Potentilla vulcanicola is widespread here in alpine and arctic parts of Alaska, Yukon Territory, western Northwest Territories to east of the Mackenzie River, and western Nunavut to Banks and Victoria islands. Records from south of Yukon Territory need confirmation. The species is typical of exposed alpine habitats (fellfield) but not with any clear preference for base-rich substrates. A significant portion of the records mapped by Hultén (1968) for P. uniflora belongs to P. vulcanicola (which also is the species closest to P. uniflora in morphology).

Potentilla subvahliana is more northern than the three previous species; in Alaska it is mainly found in the arctic parts south to Seward Peninsula, central parts south to southern Brooks Range, and in Yukon Territory mostly in the northern and central parts. Eastwards it extends across arctic Canada to Baffin Island, Ellesmere Island, and northwestern Greenland (where the northern half of what has been considered P. vahliana by Böcher et al. (1978), is P. subvahliana).

Potentilla subvahliana is also a species of alpine and arctic fellfield, but with a distinct preference for base-rich bedrock. It is rare in the Pre-Cambrian shield parts of the Canadian Arctic Archipelago and the more acidic mountains of Alaska. The range mapped in Alaska and the Yukon by Hultén (1968) for P. vahliana belongs to P. subvahliana, but the species is far more common than indicated by Hultén's scattered records.

Potentilla subgorodkovii is probably the most frequent entity of the group in northwestern North America: in Alaska and Yukon Territory, western Northwest Territories and Nunavut. It is the only species of the group in southern British Columbia, Alberta, and disjunct in Montana, Wyoming, and Colorado. The major part of the Alaskan and Yukon records of "P. uniflora" probably belong to P. subgorodkovii, and perhaps all records from farther south also.

Potentilla subgorodkovii is more wide-ranging ecologically, from coastal habitats to alpine meadows, fellfield and outcrops, and from very acidic to very basic bedrock. It is not intermediate between the P. nivea and the P. uniflora group in ecological preferences but spans both ranges. The major part of what Cody (1996, 2000) mapped as P. villosula in Yukon Territory probably belongs to P. subgorodkovii.

The acceptance of these five species, and of the hybridization hypothesis behind three of them, is based on morphology alone. Experimental investigations are urgently needed. Some investigations have addressed the question (Eriksen & Töpel 2006; Töpel et al. 2006), but they have applied a very broad species circumscription and necessarily concluded that the "species" are variable.


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Eriksen, B. & Töpel, M.H. 2006.
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In: IOPB Chromosome number reports XXV. – Taxon 19: 102–113.
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In: IOPB Chromosome number reports LXXV. – Taxon 31: 342–368.
Soják, J. 1985.
Some new northern hybrids in Potentilla L. – Preslia 57: 263–266.
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Notes on Potentilla. I. Hybridogenous species derived from intersectional hybrids of sect. Niveae and sect. Multifidae. – Bot. Jahrb. Syst. 106: 145–210.
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A.N. Berkutenko Woody plants of Northern Sakhalin. Atlas-manual. 2007,
68 p., 339 colour illustrations. ISBN 5-93250-080-8 (hard cover)

This illustrated atlas is the first of its kind, and provides an introduction to the woody plants growing in the territory of 3 forestry enterprises: Noglikskyi, Ochinskyi and Aleksandrovskyi, located on the north Sakhalin and occupying 2,533,000 ha. 260 photos taken by the author during field expeditions allow the reader to identify 84 species of woody plants: trees, vines, shrubs, dwarf shrubs and half shrubs occurring in the northern part of Sakhalin. The photos are accompanied by text on the characteristics of morphological features, information on ecology, biological peculiarities, chromosome numbers, date and location of species description, and distribution outside the Russian Far East. Distribution maps of 75 species in the Russian Far East are provided. The book is primarily targeted to specialists in forestry, but is also useful to ecologists, geographers, environmental specialists, teachers, students, schoolchildren and all those who would like an introduction to the northern wilderness in one of the most remote regions of Russia.


A.N.Berkutenko, A.F.Semenin. (2007)
Herbaceous Wild Plants of Urals. Ekaterinburg, Sokrat Publishing House. 160 p. ISBN 5-88664-223-4 (hard cover) Semipopular book with 143 color original photos. Some species are illustrated for the first time. Text is in Russian.

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