Flora of North America species comparison

Amelanchier arborea is distinctive for its arborescent habit, generally precocious flowering, leaf margins each with (3–)5–9(–13) teeth on distal cm, densely hairy abaxial surface of leaf blades, and strongly reflexed sepals at flowering. Leaves typically have subcordate to strongly cordate bases, acuminate apices, and margins sometimes finely double serrate.

The name Amelanchier canadensis was applied by many botanists to A. arborea and A. laevis until M. L. Fernald (1941) clarified the issue; this usage appears in some older manuals. McKay transferred A. laevis to subspecific status under A. arborea, and the two species are generally considered to be closely related. Allozyme data show that, with one exception, populations of each are more closely related to a nearby population of the other than they are to conspecific populations (R. D. Overath and J. L. Hamrick 1998). At flowering, A. arborea and A. laevis can be distinguished by leaf color, which is typically reddish green or reddish brown in A. laevis and green to greenish white in A. arborea. In addition, the leaves of A. laevis are at least half-expanded and unfolding as well as glabrous (or sparsely hairy) by flowering, and its sepals are spreading to reflexed.

Amelanchier arborea exhibits considerable variation; infraspecific taxa have been named. Variety alabamensis differs in its densely hairy ovary apices. Variation in ovary summit indument in A. arborea does not appear to be associated with any other taxonomically informative variation; individuals with varying amounts of ovary indument occur sporadically in populations; this does not appear ecologically significant. The authors conclude that this variety does not warrant taxonomic recognition; they have observed groups of populations that differ in the number of flowers per inflorescence, color of the expanding leaves, size of the teeth, and other features.

Amelanchier arborea usually flowers a week or more before sympatric congeners. The species has been reported (M. L. Fernald 1950) to hybridize with A. bartramiana, A. canadensis, A. humilis, and A. laevis. The authors have collected putative hybrids with A. amabilis in New York and have observed putative hybrids between A. arborea and other eastern North American species of Amelanchier. Hybrid swarms in New Jersey between this species and A. laevis but not A. canadensis have been reported (J. E. Cruise 1964).

(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.)