Panarctic Flora

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641055 Potentilla hyparctica Malte

GBIF

2n= (1) 28 (4x). - Siberia (N), Far East (N). - At least three reports, numerous counts, mostly for subsp. nivicola.
(2) 42 (6x). - Europe (N), Siberia (N), Far East (N), Alaska, Canada, Greenland. - Numerous reports.
(3) 49 (7x). - Far East (N), Canada (E). - Three reports, one Russian for subsp. nivicola.

Geography: Circumpolar.

Notes: Yurtsev, Murray, Elven, and Aiken: We agree that Potentilla hyparctica s. lat. is a complex of several races or species but we do not agree on its subdivision. The complex has been treated in different ways in northwestern Europe and North America (including Greenland) on one side and in Russia on the other.

Name. - Elven and Murray: This species was known as P. emarginata Pursh 1813 until Fernald (1943) showed that name to be a homonym of P. emarginata Desf. 1804. Since then, P. hyparctica Malte 1934 has been nearly uniformly accepted as its name. However, three older names have been discussed: P. groenlandica, P. nana, and P. robbinsiana.

Potentilla groenlandica R. Br. 1819, based on Greenland material, refer to this species but is a nomen nudum and has, as far as we know, never been validated.

Potentilla nana Willd. ex Schltdl. 1813-1816 was included in P. hyparctica by Hultén (1946) but is rather another species, perhaps a hybrid species developed from cross(es) between P. fragiformis x P. hyparctica, see below.

Potentilla robbinsiana "Oakes in Torr. & A. Gray, Fl. N. Amer. 1: 441 (1840)" [P. hyparctica Malte subsp. robbinsiana ("Oakes") Á. Löve & D. Löve, Taxon 13: 204 (1964)] was described from the White Mountains in New Hampshire, U.S.A. This is a southern marginal population group of the P. hyparctica complex. As stated by K. Gandhi (in comment), the citation above is invalid but the first valid combination as a species still well predates P. hyparctica Malte 1934: P. robbinsiana (Lehm.) Rydb., Bull. Torrey Bot. Club 23: 304 (1896), based on P. minima var. robbinsiana Lehm., Revis. Potent.: 159 (1856). The strange recombination by Löve and Löve (1964b) as P. hyparctica subsp. robbinsiana is contrary to the Code as the species name P. robbinsiana has priority (1896) well before P. hyparctica (1934). Doris Löve later made the formally correct combination P. robbinsiana subsp. hyparctica. The relationship between P. hyparctica and P. robbinsiana was described by Löve and Löve (1965) who interpreted the White Mountains plants as small, depauperate, and slightly deviating populations, probably agamic (2n = 49; Löve and Solbrig 1964b, Löve and Löve 1966), of the more widespread arctic species, i.e., as a subspecies. It is now accepted as an endangered 'flag' species of the White Mountains.

Variation. - Elven, Murray, and Aiken: There has been no circumpolar study of the morphological or molecular variation of P. hyparctica. Regional studies in northern Asia and North America (including Greenland) have given different results and are not fully comparable. Yurtsev (PAF proposal) accepted two subspecies: subsp. hyparctica throughout and subsp. nivicola from Siberia, the Russian Far East, and Alaska. For distinctions and keys, see Yurtsev (1984b) and Kurbatskij (1988). It may be worth notice that tetraploids (2n = 28) are documented only from northern Asia and mainly reported for subsp. nivicola, whereas hexaploids and higher levels occur throughout.

Elven and Aiken revised the material from northern Canada (CAN, DAO) in 2000-2001 for the Flora of the Canadian Arctic Archipelago (Elven 2007). They then recognized two races: a widespread high-arctic Entity I to which the type of the name P. hyparctica Malte belongs, and a widespread low-arctic Entity II to which the names P. emarginata Pursh and var. elatior Abrom. belong. Elven and Murray in Murray and Elven (2007) recombined Entity II as P. hyparctica subsp. elatior. The two races slightly overlap geographically but differ disjunctly morphologically in the meeting zone, a few times within sites as in southern Baffin Island. No transition is observed and none of the morphological differences seem to be clinal or adaptive. The northern subsp. hyparctica is more slender and small-grown than the southern subsp. elatior, more hairy, with leaflets much more dissected and with much more acute lobes (vs. crenate), and with small, narrow and more acute calyx and epicalyx segments (vs. large and sometimes suborbicular). The petals thereby appear larger compared with the sepals. Subspecies hyparctica predominates in the high-arctic material from other regions (Greenland, Europe, Siberia, Alaska, the Yukon Territory). We have only seen fully characteristic subsp. elatior from Canada and from Greenland north to Disko. A var. elatior has frequently been accepted as a taxon in North America and Greenland. The epicalyx and sepal characters distinguish subsp. elatior from subsp. nivicola in northeastern Asia.

Murray and Elven revised the Alaskan and Yukon Territory material (ALA) in preparation for the Flora of North America treatment (Ertter et al. 2011). They found some support for occurrence of two races: hyparctica s. str. and a race combining features of subsp. elatior and the northeastern Asian subsp. nivicola. They did not find the differences between subsp. hyparctica and subsp. nivicola as clear as suggested on the Russian side. The choices are then: (a) One collective species without subdivisions, (b) three subspecific taxa, subsp. hyparctica, subsp. nivicola, and subsp. elatior and the majority of the plants in Alaska and the Yukon Territory as either subsp. nivicola or subsp. elatior, or (c) three species, possibly supported by the absence of observed intermediates and transitions between "hyparctica" s. str. and "elatior" in Canada and Greenland and a suggested ploidy difference between subsp. nivicola and the two others.

Yurtsev: Potentilla hyparctica is a meta-arctic species most common throughout the Arctic, especially at higher latitudes. Limitation is caused, however, by a certain preference for acidic (to subneutral) rocks. In Yurtsev (1984b) some regularities in the geographic variation of the species are described in many details (but in Russian). More than two regional races are recorded but only one of them (mostly tetraploid, 2n = 28) was formally described as subsp. nivicola (it was earlier taken for P. gelida due to leaf dissection etc.). Potentilla hyparctica, no doubt, reveals strong zonal variation in growth form and other characters. Thus, one can easily determine in which group of subzones: arctic (A-C) or hypoarctic the plant grew. Associated characters are density and length of pubescence and the relation between increasing length and width in the process of growth of leaflets, their segments, sepals and epicalyx segments. So, I do not think that the proposed entities by Elven and Aiken i.e., subsp. [hyparctica and subsp. elatior] do not reflect zonal conditions (of course, it probably involves not only modification). Then as we move northwards, the ratio between development of vegetative and generative organs shifts towards that of the generative. The same occurs in the Russian Arctic: it is a circumpolar phenomenon, and hardly needs describing as two taxa.

Elven, Murray, and Aiken: Even if Yurtsev expressed his doubts in a polite way, it is obvious that he was reluctant to accept the racial differentiation we found in Canada. We suspect that his doubts can be explained by little or no material available to him for study from Canada and Greenland. We disagree with him as the described Canadian variation is disjunct, not clinal, and sometimes found within sites, as the differential characters are not of a modificative kind and concern several organs, and as a similar differentiation has not been observed (or described) in Russian material.

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