Panarctic Flora

641026 Potentilla villosa Pall. ex Pursh

• Pursh, Fl. Amer. Sept. 1: 353 (1813). Described from the "northwest coast of North America" (Alaska).

2n= 14 (2x). - Alaska, Canada (W). - At least four reports.
Not included: A report of 2n = 14 from the Chukchi Peninsula (Zhukova 1965a) is from outside the accepted geographical range. We also omit some old reports of higher ploidy levels under the name P. villosa: 2n = 42 (6x; Müntzing 1931; Popoff 1939) and 49 (7x; Müntzing 1931).

Geography: Amphi-Pacific: ALA.

Notes: Potentilla villosa reaches the Arctic along the Bering Sea coast in southwestern Alaska.

Yurtsev: North-Pacific P. villosa is plant of sea coasts and cliffs. It is a diploid species, probably an ancient one, and differs from the boreal oceanic species P. villosula in much larger leaflets with smaller and more numerous teeth, with upper side of them densely covered with light golden, adpressed, short hairs, lucideous (non loosely and longer pilose, teeth longer); inflorescences many-flowered, flowers larger with much more numerous stamens; and pistils conical. Petioles are shortly tomentose throughout and adpressed pilose.

Elven and Murray: Applying the keys of Yurtsev (1984b) and Soják (2004) to northwestern North American material, we found that the specimens were divisible into three morphologically separable groups. Two of these corresponded to P. villosa s. str. and P. villosula as described in these keys. A large third group, also fairly consistent morphologically, combined several features from P. villosa s. str. and P. villosula: silky pubescence as in P. villosa; leaf teeth less numerous and less rounded than in P. villosa but more numerous and obtuse than in P. villosula s. str.; flowers less numerous and often smaller than in P. villosa, with longer pedicels, but more similar to that species than to P. villosula in, e.g., their broader bracts; and achenes often with a few apical hairs as in P. villosula. The third, unnamed plant is generally sympatric with P. villosa but mostly found in alpine, not maritime sites. As it has more features in common with P. villosa than with P. villosula, we have provisionally assigned it to the former rather than to the largely allopatric P. villosula, which would be the solution if we applied only Soják's key characters. This choice is arbitrary. The arctic range of these P. villosa-villosula intermediates is nearly the same as for P. villosa, i.e., southwestern Alaska, even if they usually are separated vertically at a local scale. We suspect that this third group may be a third species.