Panarctic Flora

641037 Potentilla prostrata Rottb.

• Rottb., Skr. Kiøbenhavnske Selsk. Lærd. Elsk. 10: 453 (1770). Described from western Greenland. Internal note: Search Soják's papers for more specific type information.
• Potentilla nivea var. subquinata Lange, Consp. Fl. Groenland.: 9 (1880). Lectotype (C!): Greenland: Disco, Quannersuit, 23. June 1871, leg. Th.M. Fries. Internal note: Search Soják's papers for place of lectotypification. - Potentilla subquinata (Lange) Rydb., Monogr. N. Amer. Potentill.: 76 (1898). - Potentilla nivea subsp. subquinata (Lange) Hultén, Bot. Not. 1945: 135 (1945).
• Potentilla mischkinii Juz., Fl. Murmansk. Obl. 4: 323, 76 (1959). Holotype (LE): European Russia: the Murman area, "montes Chibinenses in declive meridionali Poatschvumtschorr ...", 27. July 1946, leg. B. Mischkin 111. - Potentilla nivea subsp. mischkinii (Juz.) Jurtz., Fl. Arct. URSS 9, 1: 173 (1984).

2n= See notes. Some reports for P. nivea may belong here.

Geography: Amphi-Atlantic: NOR RUS SIB? CAN GRL.

Notes: Elven: Concerning this plant or group, the opinions of Soják and Yurtsev differ markedly from those of Elven reflected in the present version for the Checklist.

Three species names seems to belong to plants combining characters from Potentilla arenosa subsp. chamissonis and P. nivea. (1) Soják (2004) identified P. prostrata Rottb. 1770 with P. chamissonis x P. nivea and accepted a hybrid species. (2) Soják (1986, 2004) and Yurtsev (PAF proposal) interpreted P. subquinata (Lange) Rydb. 1898 to have developed from cross(es) between P. nivea and P. pulchella, due to the occasional presence of more than three leaflets, but we find it to combine features of P. arenosa subsp. chamissonis and P. nivea. See further below. (3) Potentilla mischkinii Juz. 1959 was described and illustrated as intermediate between P. chamissonis and P. nivea (Juzepczuk 1959a: 76, t. XXIV, 323-324). Two questions need to be answered: whether the parental combinations safely can be presumed to be the same for P. prostrata, P. subquinata, and P. mischkinii (if hybridogeneous), and whether these names represent morphologically different taxa in spite of the same presumed parents. We here presume that they are hybridogeneous from the same parental combination and that the morphological variation pattern does not justify several taxa (perhaps not even one).

Potentilla mischkinii. - Yurtsev: Whereas P. nivea subsp. nivea has leaflets broadly cuneate (the lateral ones often somewhat overlap with the terminal one), teeth shorter and rounded to acutish, and epicalyx segments oblong-lanceolate and mostly obtuse, subsp. mischkinii has leaflets more narrowly cuneate and non overlapping (the middle one sometimes on short petiolule), teeth longer and triangular or narrowly triangular, and epicalyx segments lanceolate or narrowly lanceolate and acute. Subspecies nivea usually has only floccose hairs on petioles and veins, whereas subsp. mischkinii more often also has straight or flexuose hairs (verrucose according to Eriksen and Yurtsev 1999). Thus, this character is not constant. Presence of verrucose straight hairs on leaves of P. mischkinii votes for its hybrid origin with [P. arenosa s. lat. in its parentage].

Elven and Murray: As suggested by Yurtsev above and supported by us, the name P. mischkinii probably belongs to offspring from hybridization between P. arenosa subsp. [chamissonis] and P. nivea. It is thereby not acceptable as name for a widespread race of P. nivea. Potentilla mischkinii was described from the single, isolated population assigned to P. nivea in the Khibiny Mountains in the Murman area, whereas the more frequent plant in this region is P. arenosa subsp. chamissonis. The type population of P. mischkinii is at the margin of the Fennoscandian range of P. nivea. Its reported features are such that characterize hybrids between P. arenosa subsp. chamissonis and P. nivea. Such hybrids have been proved from very numerous places in Fennoscandia, often as populations, and are also evident in the molecular data of Nyléhn et al. (unpubl.). Yurtsev stated that subsp. mischkinii was the race of northern Fennoscandia (see also Yurtsev 1984b). The northern Fennoscandian plants mainly belong to the type race, i.e., P. nivea s. str. (Nyléhn et al. unpubl.). Soják (2004) synonymized P. mischkinii with P. prostrata (excluding subsp. floccosa) and considered it a hybrid species developed from cross(es) between P. chamissonis and nivea. We agree with the hybrid hypothesis but are not sure that it can be fully justified as a stabilized hybrid species. The Fennoscandian pattern rather suggests primary hybrids and hybridogeneous biotypes here and there, without a consistent geographical pattern and with little spatial separation from the presumed parents.

Potentilla subquinata. - Elven, Hamre, and Nyléhn: The lectotype chosen by Soják (1986) for P. subquinata has, according to Yurtsev, a combination of ternate leaves with one digitate and one shortly pinnate. We (Hamre and Elven in 2003, Elven in 2011) have re-inspected the material annotated by Soják as P. subquinata (in C). The lectotype specimen has deeply dissected leaflets, a distinctly stalked ("petiolulate") terminal leaflet, and a mixed petiole pubescence of short floccose and very numerous long, straight and strongly verrucose hairs. The petiole hairs in the lectotype specimen of P. subquinata differs from those in all other hybrid species we know of with participation of P. pulchella in their parentage. Neither is any influence from P. pulchella visible in blade dissection or pubescence or in inflorescence or flowers. The inflorescence and petiole hair characters rather tell that this specimen is a hybrid (probably a primary one) between P. nivea and P. arenosa subsp. chamissonis. The other specimens among the original material for the name P. subquinata are of mixed characters: the collection from Upernivik, Aug. 1834, is pure P. nivea, whereas the collection from Claushavn, 6. July 1867, is a mixture of P. nivea and P. arenosa x nivea (i.e., P. subquinata). The other Greenland specimens (in C) annotated or sorted as P. subquinata are mostly P. nivea. The material from C does not suggest that P. subquinata is a consistent taxon in Greenland, rather scattered primary hybrids or small swarms. We confidently synonymize P. subquinata with P. prostrata.

How the name "subquinata" has been applied is a different matter. Hultén (1945b) assigned all plants from Svalbard and some from arctic mainland Norway to P. subquinata (as P. nivea subsp. subquinata), as did Rydberg (1908) with some plants from northeastern North America, Hultén (1968a) with some from northwestern North America, and Yurtsev (1984b) with some from Russia. Potentilla subquinata was accepted from Svalbard as late as by Kurtto et al. (2004). Occasional supernumerary leaflets occur with some frequency in otherwise quite normal P. nivea (type race) both in southern Norway, northern Fennoscandia, and Svalbard. However, the arctic mainland Norwegian plants assigned to P. subquinata (and probably the Murman area plants included by Yurtsev 1984b) really have an irregular number of leaflets but no relationship with Greenland P. subquinata and no discernible influence from either P. arenosa or P. pulchella. They rather have pubescence, leaflet shape, and glands strongly indicative of hybridization with P. crantzii (sect. Aureae). Such putative hybrids (P. crantzii x P. nivea) are known from at least four other parts of Scandinavia (Elven et al. 2005). They form good populations, have a certain range, and they would obviously deserve a species name in the approach of Soják and Yurtsev. We enter them below as a Potentilla sp. "Varanger" under sect. Aureae x sect. Niveae. The Svalbard plants assigned to P. subquinata are nearly uniformly ternate like P. nivea s. str. They have been investigated both morphologically and by molecular markers (Nyléhn 1999; Hamre 2000; Hansen et al. 2000; Nyléhn et al. unpubl.). In both aspects they group closely together with the majority of Scandinavian P. nivea including its type (Nyléhn et al. unpubl.). Svalbard P. "subquinata" belongs to P. nivea subsp. nivea. The northeastern North American plants we have seen annotated as P. subquinata (CAN, DAO) are rather stray plants of P. nivea with supernumerary leaflets or occasional hybrids of diverse origins. The northwestern North American plants assigned to P. subquinata (ALA) are misidentified P. nivea.

Potentilla prostrata. - We agree with Soják's (2004) interpretation of this plant as offspring from hybridization between P. arenosa subsp. chamissonis and P. nivea and also with his application of this name as the priority one for such combinations.

Chromosome numbers. - There are several reports of chromosome numbers assigned to P. mischkinii or P. nivea subsp. mischkinii (Zhukova and Petrovsky 1985b: 2n = 28 (4x) from West Chukotka, six counts; 2n = 42 (6x) from South Chukotka; 2n = 56 (8x) from West and South Chukotka and Wrangel Island, ten counts; and 2n = 70 (10x) from northeastern Yakutia and South Chukotka). All these are from outside the geographical range we accept for P. prostrata (= P. mischkinii, = P. subquinata). They should be checked against P. nivea and P. drymeja, the tetraploids perhaps also against P. crebridens subsp. hemicryophila. The reason for these Beringian reports is that Yurtsev (1984b and later) assigned all arctic plants of P. nivea as subsp. mischkinii.