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 nitens is rarely found outside of pinyon pine-juniper community types; it often grows adjacent to seasonal streams and washes. The species is distinguished by its lustrous and coriaceous leaves (particularly in lower elevation populations), moderately hairy twigs, usually salmon-colored bark on older branches and trunks, relatively short inflorescences, and (typically) three styles. Petioles on many live specimens are a bright, lustrous red, a character state that is less noticeable on herbarium specimens. Stems are usually highly contorted, with relatively short internodes, abundant short shoots, and, often, divaricately branching ultimate branches. Seeds of A. nitens are much larger than congenerics (a sample of 25 averaged 7.3 times heavier than 25 seeds from an average eastern North American Amelanchier).

The authors have observed incomplete herbarium specimens conforming to Amelanchier nitens (1923) morphology from Colorado, New Mexico, and Utah, including the type specimen of A. rubescens Greene (1900), which may prove to be the correct name for this species.

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