Panarctic Flora


580248-50 The Salix phylicifolia aggregate S. phylicifolia, S. planifolia, S. pulchra

Geography: Circumboreal-polar.

Notes: Argus and Elven: This is an aggregate of three fairly closely related taxa. Hultén (1968a) recognized a S. phylicifolia subsp. planifolia. Some collectors have annotated specimens of S. phylicifolia from Iceland as S. planifolia (in herb.). Argus (1973) recognized a S. planifolia subsp. pulchra (Cham.) Argus. We accept three species: S. phylicifolia, S. planifolia, and S. pulchra.

Salix planifolia differs from S. phylicifolia in branches and branchlets (twigs) often densely villous, juvenile and mature leaf blades and petioles often hairy with white and rust-colored hairs, stipules usually present, and stipes (pedicels) usually shorter (0.3-0.8 vs. 0.8-2 mm long). Salix pulchra differs from S. planifolia in its prominent, linear to lanceolate stipules, often persistent for two or more years and generally equal to or exceeding the petioles, and juvenile leaves usually glabrous or sparsely pubescent. Salix phylicifolia differs from the other two species in catkins usually born on longer flowering branchlets 3-6 (20) mm long vs. 0-2.5 (5) mm. There seems to be a difference also in ploidy levels. Salix phylicifolia is mostly reported to be hexaploid (2n = 114), S. pulchra and S. planifolia are both reported to be tetraploids (2n = 76). Where S. planifolia and S. pulchra overlap in the Mackenzie River basin, there is some evidence of hybridization but species distinctions are not compromised.

Our reasons for treating them as species are that each of them seem to be distinguished by a number of characters, that the areas of overlap are small, and that intergradation is limited even where they overlap. Intergradation is much more evident with some more distantly related species, e.g., for S. phylicifolia with S. glauca, S. lapponum, S. myrsinifolia, and S. starkeana in Fennoscandia.

Higher Taxa