Flora of North America species comparison

Elymus lanceolatus grows in sand and clay soils and dry to mesic habitats. It is found primarily in the western half of the Flora region, between the coastal mountains and 95° W longitude, with the exception of E. lanceolatus subsp. psammophilus, which extends around the Great Lakes. Three subspecies are recognized, primarily on the basis of their lemma and palea pubescence.

Elymus lanceolatus is primarily outcrossing, and hybridizes with several species of Triticeae. Elymus albicans (p. 334) is thought to be derived from hybridization with the awned phase of Pseudoroegneria spicata (p. 281). Judging from specimens of controlled hybrids, hybridization with E. trachycaulus (p. 321) and unawned plants of P. spicata probably occur, but would be almost impossible to detect without careful observation in the field. Experimental hybrids are partially fertile, and capable of backcrossing to either parent (Dewey 1965, 1967, 1968, 1975, 1976).

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

Elymus trachycaulus grows from sea level to 3300 m, usually in open or moderately open areas, but sometimes in forests. Its range extends from the boreal forests of North America east through Canada to Greenland and south into Mexico. It also grows, as an introduction, in Asia and Europe. It exhibits considerable variability in the presence or absence of rhizomes, the length and density of the spike, awn development on the glumes and lemmas, and glume venation. The variability in these features has often been used to circumscribe infraspecific taxa, but most such taxa, even though locally distinctive, appear to intergrade. Some of the features appear to be strongly influenced by environmental factors. For instance, plants growing in forested areas of northwestern North America tend to be slightly rhizomatous, more gracile, and later-flowering that those in adjacent, more exposed areas; whether they constitute a distinct taxon or merely a forest ecotype is not clear. Plants growing at higher elevations tend to have glumes with more widely spaced veins and broader, often unequal margins, resembling E. violaceus in these respects. Whether this reflects ecotypic differentiation, hybridization with E. violaceus (p. 324), or greater genetic continuity than is suggested by their placement in different species is not clear.

Jozwik (1966) recognized four groups within Elymus trachycaulus. Group I comprised unawned or shortly awned specimens; group II a polymorphic assemblage of awned specimens; group III a rather homomorphic group of specimens with secund spikes and relatively long awns; and group IV a relatively homomorphic group of unawned, high-elevation specimens. He concluded that group II consists of hybrids and backcrosses between E. trachycaulus and other species of Triticeae. He based this conclusion on consideration of field observations, artificial hybrids, the polymorphism of the specimens, and the geographic distribution of the group. This last was similar to that of unawned specimens of E. trachycaulus, but the populations were highly scattered within the area concerned. Jozwik's group III is treated here as E. trachycaulus subsp. subsecundus. His group IV is treated here as E. violaceus.

Elymus trachycaulus is often confused with E. stebbinsii (p. 329). It differs in having shorter anthers, shorter internodes, and glumes that are sometimes awned. It may also be confused, particularly in the herbarium, with specimens of E. glaucus having solitary spikelets at all the spike nodes; it usually differs in having shorter anthers and less acuminate glumes. When, as is sometimes the case, the two species grow together, E. trachycaulus can be distinguished by its stiffer leaves. Elymus trachycaulus also resembles E. macrourus (p. 324) and E. alaskanus (p. 326), but its glumes are longer relative to the lemmas. It also has less hairy rachillas than most plants of those species.

C.L. Hitchcock et al. (1969) treated Elymus trachycaulus as a subspecies of E. caninus (see next); it differs consistently from the latter species in glumes that are glabrous on the adaxial (inner) surface, in a chromosome interchange, and in its molecular characteristics (Sun et al. 1998). It also tends to have a more erect spike.

Elymus trachycaulus has been implicated in several interspecific and intergeneric hybrids. Named interspecific hybrids (pp. 338-343) (and the other parent) are E. ×cayouetteorum (E. canadensis), E. ×palmerensis (E. sibiricus), E. ×pseudorepens (E. lanceolatus), and E. ×saundersii (E. elymoides). Hybrids with E. hystrix have been named ×Agroelymus dorei Bowden; the appropriate combination has not been made in Elymus. Named intergeneric hybrids are ×Elyhordeum macounii (p. 284) (Hordeum jubatum), ×Elyleymus jamesensis (p. 348) {Leymus mollis), and ×Elyleymus ontariensis (p. 346) (Leymus innovatus). Hybrids with Elymus elymoides, E. multisetus, and Hordeum jubatum have brittle rachises and tend to be awned. Others are harder to recognize.

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