Chromosome numbers of some North American Arctic and Boreal Salix

Abstract

Chromosome numbers are reported for 12 native North American species of Salix and one natural hybrid. The arctic species Salix alaxensis var. alaxensis, S. fuscescens, S. ovalifolia var. ovalifolia, S. phlebophylla, and S. reticulata and the boreal species S. arbusculoides are diploids, 2n = 38. Tetraploid counts, 2n = 76, are reported for the arctic S. planifolia ssp. pulchra. Taxa with more than one chromosome number include S. planifolia ssp. planifolia and S. pedicellaris, each of which has tetraploid and triploid levels; S. arctica s.l., which is tetraploid in the eastern American arctic and hexaploid in the Alaska and Eurasian arctic; and S. athabascensis with triploid, tetraploid, and hexaploid levels. Intra-population variation in chromosome number is reported for S. glauca in which tetraploids, pentaploids, and hexaploids occur in a single Alaskan population.