keys to the vascular plants of east texas - Botanical Research ...

924 POACEAE/ELYMUS
controversial and in flux). A narrow treatment would exclude species sometimes separated into
genera such as Elytrigia, Hystrix, Pascopyrum, and Sitanion, while a broad view would include
these. Because of a variety of genetic/molecular evidence (e.g., Jaaska 1998), we lean toward the
broader view. The genus is complex and diverse—this diversity “probably stems from a combination
of multiple origins involving different progenitors, introgression within the genus,
hybridization with other members of the tribe, and plasticity. Little is known concerning the
relative importance of these factors” (Barkworth & Campbell ined.). Recently, Helfgott and
Mason-Gamer (2004) suggested that the genus is an allopolyploid derivative of Pseudoroegneria
and Hordeum. It is an understatement to say there is a diversity of opinion about generic concepts
in the Triticeae (Elymus, Hordeum, Secale, Triticum, and their relatives). Barkworth (2000)
gave a detailed history of the changing views of generic relationships within the tribe. It is particularly
important to realize that the Triticeae has an extremely complex evolutionary history
involving hybridization, polyploidy, and reticulate evolution; even some of the diploid members
of the tribe are apparently polyphyletic in origin (Barkworth 2000; Mason-Gamer &
Kellogg 2000). This complexity is emphasized by the fact that different molecular studies give
quite different and conflicting results (Mason-Gamer & Kellogg 2000). In fact, Barkworth
(2000) said that “ … I do not see there ever being complete agreement on the generic treatment of
the tribe because of the complexity of the phylogenetic relationships within the tribe.” Further,
intergeneric hybrids are known between Elymus and Tr iticum (Watson & Dallwitz 1992), and
one of the genomes in many polyploid species of Elymus is derived from Hordeum (Barkworth
& Campbell ined.). While realizing these problems, we are nonetheless faced with choosing the
best way to treat five East TX species. Three (E. canadensis, E. villosa, E. virginiana) belong to
Elymus without controversy. Elymus repens has been variously treated in either Agropyron,
Elytrigia, or Elymus, but based on genetic data (e.g., Assadi & Runemark 1995), we agree with
Yatskievych (1999), Barkworth (2000), and Barkworth and Campbell (ined.) on treating it in
Elymus. Finally, E. smithii (variously treated in Agropyron, Elymus, Elytrigia, or the monotypic
genus Pascopyrum) appears to be a hybrid involving species considered by many authorities to
be in Elymus (see further discussion under the species). It therefore seems most sensible to include
it in Elymus as well. (Ancient Greek name for millet; from elyo, rolled up, from the caryopsis
(= fruit) being tightly embraced by the lemma and palea) (subfamily Pooideae, tribe
Triticeae)
REFERENCES: Pohl 1959; Gillett & Senn 1960; Bowden 1964; Church 1967; Runemark & Heneen
1968; Dewey 1975, 1982, 1983; Baum 1979; Davies 1980; Löve 1980; Estes & Tyrl 1982; Gabel 1984;
Gupta & Baum 1989; Assadi & Runemark 1995; Campbell 1996; Tucker 1996; Jaaska 1998;
Seberg & Petersen 1998; Barkworth 1997, 2000; Mason-Gamer & Kellogg 2000; Mason-Gamer
2001; Barkworth & Campbell ined.
1. Spikelets usually 1 per node of inflorescence, sometimes 2 at middle and lower nodes of inflorescence;
lemma awn absent or 10 mm or less long.
2. Leaf blades usually involute (= the margins inrolled), stiff, the widest ones usually less than 5
mm wide (even when unrolled); foliage usually not glaucous, dark green to somewhat bluish
green; glumes 2–3 mm wide, elliptic-lanceolate_________________________________________ E. repens
2. Leaf blades flat, flexible, the widest ones 3–12(–18) mm wide; foliage glaucous, blue-green;
glumes 0.5–1 mm wide, linear _______________________________________________________ E. smithii
1. Spikelets 2–3 per node of inflorescence; lemma awn 5–50 mm long.
3. Glumes strongly 3–8-ribbed above base, 1–2.5 mm wide near middle, often strongly bowed
out at base, often yellowish, hardened or rounded basally, with awn shorter than or equaling
the body; lemma awns straight or slightly curved, 5–25 mm long _______________________ E. virginicus
3. Glumes strongly 1–4-ribbed to base or nearly so, 0.2–1.5 mm wide near middle, not or only
slightly bowed out at base, flat, neither yellowish, hardened, nor rounded basally, with awn
equaling or exceeding the body; lemma awns usually curving outward at maturity, 15–50
mm long ___________________________________________________________________ E. canadensis