Panarctic Flora

641008-12 The Potentilla pensylvanica aggregate P. bipinnatifida, P. litoralis, P. nudicaulis, P. pensylvanica, P. sp. aff. pensylvanica

Geography: Nearly circumboreal.

Notes: The Potentilla pensylvanica aggregate is a mainly temperate-boreal group widespread in North America and Siberia and also presen in southwestern Europe, with a complicated morphological pattern. Yurtsev proposed to follow the treatment of Soják (1987). This is made problematic by Soják only treating the Eurasian variation, whereas a major part of the aggregate is American, and by discrepancies between the accounts of Soják (and Yurtsev, PAF proposal) and the American revisions by Kohli and Packer (1976) and Ertter in Ertter et al. (2011).

Kohli and Packer divided the northernmost North American material of P. pensylvanica s. lat. on two species - the mainly tetraploid P. pensylvanica s. str. and the octoploid P. bipinnatifida - and they did not comment on P. litoralis. Yurtsev proposed three species for arctic North America - P. pensylvanica, P. brooksensis, and P. litoralis - and he did not indicate to which of these should be related P. bipinnatifida. A frequently applied name for plants in Alaska and the Yukon Territory - P. virgulata - did not appear in either alternative. We accept the aggregate with 3-4 species reaching the Arctic in North America and one in Asia. We are, however, aware that the variation in Alaska and the Yukon Territory probably is larger than what is comfortably encompassed in the taxa accepted below.