Panarctic Flora

641013 Potentilla rubricaulis Lehm.

• Lehm., Nov. Stirp. Pug. 2: 11 (1830). Lectotype (PR 378170): "N. W. America", 1829, "von Hooker", Herb. Lehmann (Soják 1996: 119). See notes.
• ?Potentilla hookeriana Lehm., Del. Sem. Hort. Bot. Hamburg. 1849: 10 (1849). Holotype (PR 378171): "Amer. septentr. R Mount", leg. Burke, Herb. Lehmann.

2n= 56 (8x). - Canada (the Great Bear Lake area). - Dansereau and Steiner (1956, probably true P. rubricaulis).

Geography: North American (NW): CAN.

Notes: Elven and Murray: Soják (1996) assumed Potentilla rubricaulis to be a hybrid species from P. arenosa and P. bimundorum. We agree that it combines significant diagnostic features from these two species and that it is recognizable as a taxon.

Yurtsev: I consider P. rubricaulis as non-arctic. I examined the holotype lectotype? owing to Dr. Soják and found it very different from the arctic plants assigned under the name P. rubricaulis. It is not an arctic plant in its morphotype, with unbranched (or nearly so) caudex, not very long subappressed straight hairs (the short erect hairs layer also being present). It is by no means conspecific with the plants of the Canadian Arctic Archipelago.

Elven and Murray: Yurtsev may have been mislead by the frequent application of the name P. rubricaulis to high-arctic plants in the Canadian Arctic Archipelago, Greenland, Svalbard, and also to Alaskan plants. We agree with Yurtsev that the plants in the Canadian Arctic Archipelago (and in Svalbard, Greenland, and Alaska) are very different from and do not belong to P. rubricaulis. However, we still accept P. rubricaulis to reach the Arctic. Lehmann described P. rubricaulis from "about Bear Lake, in lat. 66" probably close to Fort Franklin in the Northwest Territories, Canada, leg. Dr. Richardson. Porsild (1955) noted that he was unable to find the plant around the assumed type locality but that he found plants very similar to the illustration and description of Lehmann at the mainland arctic coast, at Liverpool Bay, Nicholson Island (A.E. Porsild and R.T. Porsild 2905, CAN) and Cape Dalhousie (A.E. Porsild and R.T. Porsild 2774, CAN). We have studied these arctic mainland specimens and accept them as P. rubricaulis in the Lehmann meaning and as combining characters in a way consistent with the proposed hybrid origin. They comform to Yurtsev's description above.

As for the other plants assigned as P. rubricaulis, the majority of Alaskan plants fit much better inside Soják's P. psychrophila (suggested to be a hybrid species from P. litoralis x P. nivea), the plants from the Canadian Arctic Archipelago and Greenland belong to three different taxa: one yet unnamed for which we provisionally apply the name P. sp. aff. uschakovii, one we accept as P. pedersenii, and one yet unnamed for which we provisionally apply the name P. sp. aff. vahliana, and the plants from Svalbard belong to P. insularis and probably P. pedersenii or P. tolmatchevii.

Ertter: The name P. hookeriana has been extensively applied to the species entered below as P. arenosa. Soják (1996) assumed P. hookeriana to be of the same parentage as P. rubricaulis (i.e., P. arenosa subsp. arenosa x P. bimundorum) and the name to be a later synonym. We have compared these two taxa and agree that this name does not belong to P. arenosa. We are not, however, fully convinced about the synonymy with P. rubricaulis. The name P. hookeriana may belong to another, Cordilleran taxon (probably hybridogeneous) not reaching the Arctic.

Elven and Murray: Soják (1996) concluded that also the following hybrid species had a P. arenosa x bimundorum parentage: P. furcata A.E. Porsild, Bull. Natl. Mus. Canada 121: 224 (1951). Holotype (CAN): Canada: the Yukon Territory, Rose-Lapie Pass, dry, sandy slopes near Mile 102, 19. June 1944, leg. A.E. Porsild 10625 [P. hookeriana Lehm. var. furcata (A.E. Porsild) Hultén, Ark. Bot., n. s., 7, 1: 72 (1968)]. He considered it a subspecies of P. rubricaulis / P. hookeriana due to its glandular sepals and epicalyx segments. We disagree with his conclusion. Potentilla furcata does not have the inflorescence and sepal characters of P. bimundorum (which are found in P. rubricaulis) but rather features - in inflorescence shape (subcorymbose), flower size (small), and sepal glands - resembling the P. pensylvanica group. We assume it to be a hybrid species from P. arenosa x P. litoralis (or P. pensylvanica s. lat.). It is a fairly widespread and morphologically consistent regional taxon in Alaska and the Yukon Territory north to the Porcupine River, especially frequent on the dry, warm bluffs ("prairie"). It is probably acceptable as a (hybridogeneous) species. It is not yet known from the Arctic but it approaches. Potentilla furcata has been reported with 2n = 56 (Löve and Löve 1982b, Manitoba) but this count was made far outside its currently accepted range and must be rejected.

The approaches above, either that by Soják (1996) or that by Ertter et al. (2011), solve the problems concerning the troublesome name P. hookeriana. It also excludes the name P. rubricaulis as relevant for plants with semidigitate or semipinnate leaves from the High Arctic of North America, Greenland, and northwestern Europe where it has been applied regularly (e.g., Ball et al. 1968 for Svalbard; Böcher et al. 1978 for Greenland; Porsild and Cody 1980 for Canada; Rønning 1964, 1979 for Svalbard, 1996 for Greenland).