Flora of North America species comparison

Amelanchier interior is distinguished by its capacity to grow into a tree to ten meters and by having sparsely hairy young leaves that are often reddish and densely hairy ovary apices. E. L. Nielsen (1939) differentiated A. interior and A. wiegandii on the basis of leaves being carinate in A. wiegandii as opposed to flat in A. interior, and leaf sinuses rounded versus acute. G. N. Jones (1946) considered those differences to be slight, and he included A. wiegandii in A. interior. The authors follow Jones, but retain the common name Wiegand’s shadbush to commemorate Wiegand’s early insights about the taxonomy of Amelanchier. M. L. Fernald (1950) considered A. wiegandii as suggesting a small-leaved A. laevis but with shorter buds, fewer teeth, fewer veins, and summit of ovary heavily tomentose. P. Landry (1975) thought A. wiegandii to be the hybrid of A. arborea and A. sanguinea, and E. G. Voss (1972–1996, vol. 2) reasoned that A. interior is a hybrid swarm involving A. laevis (or sometimes A. arborea) and plants of the A. spicata and/or A. sanguinea complex. A hybrid origin of A. interior from A. laevis and A. sanguinea is reasonable given that stem height, the number of leaf teeth, and petal length are more or less intermediate between those two species. DNA sequences from ITS region indicate that A. interior (A. wiegandii) is a possible later-generation hybrid involving a member of the western North American ITS clade (which also includes A. humilis and A. sanguinea of eastern North America) and some eastern North American taxon (C. S. Campbell et al. 1997). Multiple hybrid origins, possibly from different species, may explain the variability of A. interior. Amelanchier interior has unusually large ranges of lengths for proximal pedicels, sepals, and petals. The leaves of A. wiegandii were described by Nielsen as bronze at flowering; Jones described the leaves of A. interior as green when young. The authors assume that A. interior as they interpret it is polymorphic for the color of young leaves.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Amelanchier bartramiana is the only North American Amelanchier with leaves that are imbricate in bud, usually fewer than four flowers per inflorescence, and conic ovary apices (and hence fruits that are more or less pear-shaped rather than globose as in other members of the genus). Because of these differences, P. Landry (1975) placed A. bartramiana in its own subgenus, and all other members of the genus in another. W. H. Blanchard (1907), W. A. Robinson and C. R. Partanen (1980), and Robinson (1982) also recognized the distinctness of this species. Amelanchier bartramiana grows farther north than any other shadbush in eastern North America, and more than other shadbushes, it occupies relatively undisturbed habitats, such as peatlands and natural breaks in mature forests. Some plants in this species produce seed sexually (C. S. Campbell et al. 1987). Sexual plants of A. bartramiana are self-incompatible diploids; a tetraploid individual has been reported (A. C. Dibble et al. 1998); it had relatively large petals and might have been an autotetraploid.

Amelanchier bartramiana usually flowers with A. laevis, and it frequently hybridizes with other members of the genus. M. L. Fernald (1950) and L. Cinq-Mars (1971) reported hybrids with A. arborea (A. ×quinti-martii Louis-Marie), A. canadensis, A. fernaldii, A. gaspensis, A. humilis, A. intermedia, A. laevis, A. sanguinea, A. spicata, and A. interior. The hybrid with A. laevis can usually be found when these two species grow together (J. E. Weber and C. S. Campbell 1989). The authors have documented a hybrid between A. arborea and A. bartramiana in eastern Pennsylvania (M. B. Burgess et al., unpubl.).

(Discussion copyrighted by Flora of North America; reprinted with permission.)