Panarctic Flora

641035 Potentilla crebridens Juz.

• Juz., Bot. Mater. Gerb. Bot. Inst. Komarova Akad. Nauk SSSR 17: 218 (1955). Described from the Irkut River in the Angara Mountains (Siberia). - Potentilla matsuokana subsp. crebridens (Juz.) Soják, Candollea 44: 752 (1989).

2n= (1) 14 (2x). - Siberia (Sayan Mountains). - Guinochet and Lefranc (1981, for P. crebridens s. str.)
(2) 28 (4x). - Siberia (SE), Asia (C). - At least three reports for P. crebridens s. str.

Geography: Asian (C-NE) - amphi-Beringian.

Notes: Yurtsev: Potentilla crebridens differs from P. nivea in, e.g., leaflet teeth short and numerous, closely congested vs. longer, fewer, and more distant; epicalyx segments filiform vs. oblong-lanceolate; style cylindrical without or with a few minute papillae at the base vs. normally thicker, subconical, with viscid papillae at base; and in being mainly or exclusively tetraploid vs. mainly hexa- or octoploid.

Since the northern boundary of P. crebridens subsp. crebridens lies far south of the Arctic, we may only comment that the northern race has some distinctions from the southern race in meadows and forest-steppes of southern Siberia and northern Mongolia (the latter with more numerous teeth on larger leaves and styles normally without papillae at the base). The northern race of hypoarctic cryophyte steppe and dry tundra is recognized as subsp. hemicryophila.

Elven and Murray: We have compared P. crebridens subsp. hemicryophila and P. nivea in material from northwestern North America, Chukotka, and northern Siberia and confirm that the characters reported above by Yurtsev reliably distinguish two taxa. The best diagnostic characters seem to be epicalyx segments linear vs. oblong-lanceolate in P. nivea, and style uniformly narrow and almost non-papillose vs. basally broadened and distinctly papillose. In addition, the shape of the leaflets and the number and shape of teeth separate the two.

Potentilla crebridens subsp. hemicryophila is sympatric with P. nivea throughout almost its entire range from northern Siberia east to northwestern Canada. The two are sometimes found in mixed stands but without observed intermediates in the investigated material (ALA, O) from Yakutia, East Chukotka, Alaska, and the Yukon Territory (se also Elven and Murray 2008c).