Flora of the Canadian Arctic Archipelago
Rosaceae, Rose family.
Vegetative morphology. Aerial stems erect, or ascending. Leaves alternate; dying annually and non-persistent, or marcescent. Stipules present. Leaf blades compound.
Reproductive morphology. Inflorescences cymose. Sepals conventional. Epicalyx present. Sepals free. Petals conventional; free; 5; slightly lobed or undulating. Stamens present; 15–30. Ovules per ovary 1.
General notes. The Potentilla nivea complex includes species named as P. nivea L., 1753, P. crebridens Juz. 1955, P. subquinata (Lange) Rydberg, 1898, P. hookeriana Lehm. 1849, P. arenosa (Turcz.) Juz. 1941, P. chamissonis Hultén 1945, P. rubricaulis Lehm. 1830, and P. pedersenii Rydberg, 1908 and others. Some of the common features of the P. nivea complex are as follows:
(1) normally trifoliate to digitate (or sub-pinnate) leaves, which distinguishes this group from the P. pulchella-multifida group, which has pinnate leaves;
(2) leaflet abaxial surfaces are very densely white-tomentose, which distinguishes the P. nivea group from P. crantzii and P. hyparctica, which both lack tomentum;
(3) adaxial surfaces are subglabrous, with scattered pilose or silky hairs in the P. nivea group, which distinguishes it from the P. vahliana-uniflora group whose plants have densely villose leaves;
(4) flowers are normally in few- to many-flowered cymes, which distinguishes the P. nivea group from the P. vahliana-uniflora group, which usually has single flowers; and
(5) the species of the P. nivea group have either floccose hairs or rough long (pilose) hairs on the petioles (or both), as opposed to the P. vahliana-uniflora group and P. pulchella, which has smooth hairs.
The arctic entities of the P. nivea complex are, as far as is known, high-polyploids, each with several ploidy levels, mostly from (4-)7-ploid to 11-ploid. They reproduce mainly by pseudogamous agamospermy. It is probable, but not proven, that the entire complex is a reticulum developed from combinations of different original diploid genomes through repeated hybridisations. As such it might be theoretically (and also practically) impossible to separate species in the traditional sense.
However, there are comparatively clear major patterns in the combinations of characters. The most evident differences are found between P. nivea s.l. (including P. crebridens), P. arenosa s.l. (including P. arenosa, P. chamissonis), and P. rubricaulis s.l. (including P. pedersenii). The P. nivea subgroup is characterised by (1) a dense floccose tomentum of comparatively short hairs on petioles and often also the flowering stems, (2) mainly ternate leaves with a sessile to sub-sessile apical leaflet, (3) leaflets being crenate to lobed with rounded approximate lobes. The P. arenosa subgroup is characterised by (1) the presence of long, stiff and mostly patent (pilose) verrucose hairs on the petioles and often also the stems, (2) mainly ternate leaves usually with stipatate apical leaflet, and (3) leaflets being dentate to usually lobed with much more acute and distant lobes. The P. rubricaulis subgroup is characterised by (1) long, soft, wavy, and silky (but verrucose) hairs on petioles and leaf surfaces, (2) ternate to digitate or sub-pinnate leaves with a sessile to sub-sessile apical leaflet, and (3) deeply lobed leaflets with approximate lobes. In addition, the P. nivea and P. arenosa subgroups have parallel-sided styles that are distinctly papillose at the base, whereas the P. rubricaulis subgroup mostly has narrowly conical styles with little evidence papillae at the base.
Soják (1985, 1986) and Yurtsev (1984, personal communication, 1999) interpreted P. pedersenii and other taxa of the P. rubricaulis subgroup as intermediate between P. pulchella and species of the P. nivea/arenosa subgroups, based on the frequent presence of digitate or subpinnate leaves in the P. rubricaulis subgroup. The entities of the P. rubricaulis subgroup differ significantly from P. pulchella hybrids in the following characters: (1) the flowers of P. rubricaulis s.l. are often larger than in the P. nivea/arenosa entities, whereas the flowers of P. pulchella and its (primary) hybrids are conspicuously small, and (2) the styles are less papillose in P. rubricaulis s.l. than in P. nivea/arenosa, whereas they are much more papillose in P. pulchella and its hybrids.
Linnaeus' original material for the name P. nivea consists of two plants. Hultén (1945) found these to be different and chose one as the holotype of his new species P. chamissonis Hultén. The original specimen most probably was collected in northern Sweden ('Lapland'). The other plant on the type sheet then, by default, became the type of P. nivea L. s.s. This second specimen is most probably from Siberia and represents what was later named as P. arenosa (Turcz.) Juz.; see Soják (1989) and Eriksen et al. (1999). It differs considerably from the northwestern European plants traditionally named as P. nivea, and more closely related to P. chamissonis. As a consequence, Soják (1989) found it necessary to find another name applicable to the northwestern European plants. Potentilla floccosa Rottb. 1770, described from Greenland, clearly belongs to the P. nivea group. Soják found differences between the Greenland type and many northeastern American and northwestern European plants and named the former as P. prostrata subsp. prostrata, the latter as subsp. floccosa Soják.
The name P. nivea has, since the times of Linnaeus, been applied consistently to northwestern European, Greenland, and (later) to northeastern American plants. Soják's proposal has therefore not been generally accepted. Following current and past usage (including Linnaeus'), Eriksen et al. (1999) proposed to conserve the name P. nivea L. with a new type from northern Sweden. This proposal is followed here. A vicariate entity occurs in the Beringian area, but perhaps not in the Canadian Arctic Archipelago. In Russian usage, the name of the Amphi-Beringian entity is P. crebridens Juz. subsp. hemicryophila Jurtz. 1984, but it might also be considered as a subspecies of a more widely defined P. nivea L.
Problems concerning the names P. arenosa versus arenosa versus chamissonis and concerning P. rubricaulis are discussed under those species.
This publication is available on the internet (posted May 2011) and on CD-ROM (published in 2007). These versions are identical in content, except that the errata page for CD-ROM is accessible on the main index page of the web version.
Recommended citation for the web-based version of this publication: Aiken, S.G., Dallwitz, M.J., Consaul, L.L., McJannet, C.L., Boles, R.L., Argus, G.W., Gillett, J.M., Scott, P.J., Elven, R., LeBlanc, M.C., Gillespie, L.J., Brysting, A.K., Solstad, H., and Harris, J.G. 2007. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. NRC Research Press, National Research Council of Canada, Ottawa. http://nature.ca/aaflora/data, accessed on DATE.
Recommended citation for the CD-ROM version of this publication: Aiken, S.G., Dallwitz, M.J., Consaul, L.L., McJannet, C.L., Boles, R.L., Argus, G.W., Gillett, J.M., Scott, P.J., Elven, R., LeBlanc, M.C., Gillespie, L.J., Brysting, A.K., Solstad, H., and Harris, J.G. 2007. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. [CD-ROM] NRC Research Press, National Research Council of Canada, Ottawa..