| BEN |
| BOTANICAL ELECTRONIC NEWS |
|---|
| ISSN 1188-603X |
| No. 390 March 12, 2008 | aceska@telus.net | Victoria, B.C. |
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[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.
The following key is based on Yurtsev (1984) and Soják (2004) but includes
some additional features and excludes characters we have found unreliable.
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.
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.
ALSO
Orders can be placed to Dr.A.Berkutenko by e-mail: berkutenko@yandex.ru
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
References
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