Panarctic Flora

610207 Betula minor (Tuck.) Fernald

• Fernald, Rhodora 47: 306 (1945). - Betula papyracea var. minor Tuck., Amer. J. Sci. Arts 45: 31 (1843). Type: U.S.A.: New Hampshire, "in alpinis Mont. Alborum" White Mountains, 1842. - Betula pubescens subsp. minor (Tuck.) Á. Löve & D. Löve, Univ. Colorado Stud., Ser. Biol. 17: 20 comb. inval..
• Betula pubescens subsp. borealis sensu Á. Löve & D. Löve, Univ. Colorado Stud., Ser. Biol. 17: 20 (1965). - Betula borealis auct., non Spach (1841).
• Betula pubescens subsp. tortuosa auct.

2n= 56 (4x). - Canada (E), U.S.A. (NE), Greenland. - Several reports for "borealis" or "minor", more than 30 counts from Greenland alone.

Geography: North American (NE): CAN GRL.

Notes: Furlow (1997) stated the relationships among the tall shrubby and partly tree-forming birches of Greenland and northeastern North America to be unresolved. Hultén (1968b) suggested that Betula minor could be a "B. glandulosa hybrid series with the eastern American tree-forming birches". Two features count against Hultén's hypothesis: its large range independent of that of the other tree-forming birches, and the large number of uniformly tetraploid chromosome counts (B. glandulosa is diploid). The last feature does not preclude introgression from B. glandulosa into a tetraploid tree-forming species, but which? Another alternative is to consider it a major northern race (subspecies) of B. pubescens, based on morphological similarities between the Greenlandic and especially the western Icelandic plants, also assuming that the vicariant B. nana may partake in the evolution of B. pubescens subsp. tortuosa. A third alternative is to accept a northwestern Atlantic species: B. minor.

Recent molecular studies (Eidesen 2007, AFLP) suggest that Greenlandic B. "pubescens" is comparatively distant from European B. pubescens (incl. subsp. tortuosa) and also less closely related to B. nana than what B. pubescens subsp. tortuosa is. A hybrid origin is not excluded but then with participation of B. glandulosa rather than of B. nana and B. pubescens.

The differences between B. minor and B. "borealis" need verification. Löve and Löve (1965) were of the opinion that their B. pubescens subsp. minor and subsp. borealis were different but intergraded, that the taxon in the White Mountains of New Hampshire was subsp. minor, whereas the plant of Labrador and Greenland was subsp. borealis. Löve and Löve (1975a) recorded subsp. borealis as the arctic birch in Greenland and northeastern Canada. However, the type of B. borealis belongs, according to Furlow (1997), to B. pumila, but the name has been applied mostly for something close to or identical with B. minor.