Further complicating matters, E. Lepage (1976) concluded that the type of Betula minor represents a hybrid between individuals of the dwarf species and B . papyrifera , and on that basis, following nomenclatural rules, he renamed the dwarf species B . saxophila , retaining the name B . minor for the hybrid. Leaf shapes and other visible characters of the type fall easily within the limits of variation of B . saxophila , however, and the group is considered here to consist of a single entity, designated by the older name B . minor .
At least in the Adirondacks, Betula minor usually occurs near populations of B . cordifolia and B . glandulosa , and it has frequently been suggested (e.g., E. Hultén 1968; E. Lepage 1976; J. J. Furlow 1990) that it may have originated through hybridization between these species (perhaps followed by polyploidy). The northern populations may similarly consist of a hybrid swarm involving B . papyrifera or B . cordifolia and B . glandulosa . Critical examination of the entire complex, including experimental studies of the patterns of hybridization present, are necessary to unravel its problems satisfactorily.