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Festuca  |
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Family: Poaceae  Cindy Roché, Illustrator |
Stephen J. Darbyshire and Leon E. Pavlick† Plants perennial; bisexual; usually densely to loosely cespitose, with or without rhizomes, occasionally stoloniferous. Culms 5–150(275) cm, usually glabrous and smooth throughout, sometimes scabrous or densely pubescent below the inflorescences. Sheaths from open to the base to closed almost to the top, in some species sheaths of previous years persisting and the blades usually deciduous, in other species the senescent sheaths rapidly shredding into fibers and decaying between the veins and the blades not deciduous; collars inconspicuous, usually glabrous; auricles absent; ligules 0.1–2(8) mm, membranous, sometimes longest at the margins, usually truncate, sometimes acute, usually ciliate, sometimes erose; blades flat, conduplicate, involute, or convolute, sometimes glaucous or pruinose, abaxial surfaces usually glabrous or scabrous, sometimes puberulent or pubescent, rarely pilose, adaxial surfaces usually scabrous, sometimes hirsute or puberulent, with or without ribs over the major veins; abaxial sclerenchyma tissue varying from longitudinal strands at the margins and opposite the midvein to adjacent to some or all of the lateral veins, longitudinal strands sometimes laterally confluent with other strands into an interrupted or continuous band, sometimes reaching to the veins and forming pillars; adaxial sclerenchyma tissuesometimes present in strands opposite the veins at the epidermis, the strands sometimes extending to the veins and, in combination with the abaxial sclerenchyma, forming girders of sclerenchyma tissue extending from one epidermis to the other at some or all of the veins. Inflorescences usually open or contracted panicles, sometimes reduced to racemes, usually with 1–2(3) branches at the lower nodes; branches usually erect, spreading to widely spreading at anthesis, sometimes the lower branches reflexed. Spikelets with (1)2–10 mostly bisexual florets, distal florets reduced or abortive; rachillas usually scabrous or pubescent, sometimes smooth and glabrous; disarticulation above the glumes, beneath the florets. Glumes subequal or unequal, usually exceeded by the florets, ovate to lanceolate, acute to acuminate; lower glumesfrom shorter than to about equal to the adjacent lemmas, 1(3)-veined; upper glumes 3(5)-veined; calluses usually wider than long, usually glabrous and smooth, sometimes scabrous, occasionally pubescent; lemmas usually chartaceous, sometimes coriaceous, bases more or less rounded dorsally, slightly or distinctly keeled distally, veins 5(7), prominent or obscure, apices acute to attenuate, sometimes minutely bidentate, usually terminally or subterminally awned or mucronate; paleas from shorter than to slightly longer than the lemmas, veins sparsely to densely scabrous-ciliate, intercostal region usually smooth and glabrous at the base, usually scabrous and/or puberulent distally, bidentate; anthers 3; ovaries glabrous or with hispidulous apices, hairs persisting on the mature caryopses. Caryopses obovoid-oblong, adaxially grooved, usually free of the lemmas and paleas, sometimes adhering along the groove, sometimes adhering more broadly; hila linear, from 1/2 as long as to almost as long as the caryopses. x = 7. Name from the Latin festuca, ‘stalk’, ‘stem’, or ‘straw’—a name used by Pliny for a weed. Festuca is a widespread genus, probably having more than 500 species. The species grow in alpine, temperate, and polar regions of all continents except Antarctica. There are 37 species native to the Flora region, 2 introduced species that have become established, and 5 introduced species that are known only as ornamentals or waifs. One species, F. rubra, is represented by both native and introduced subspecies. NOTE ADDED July 2010: Work by Catalan and her colleagues indicates that the limits of Festuca, Vulpia, Schedonorus and Lolium all need to be reconsidered. See Catalan et al 2003 and subsequent works (found using the various tools now available on the web). Many native species provide good forage in western North American grasslands and montane forests. Important cultivated species include Festuca rubra, grown for forage and as a turf grass, and F. trachyphylla, used as a turf grass and for erosion control. Both these species have been widely introduced to many parts of the world. A number of species are cultivated as ornamentals—including F. amethystina L., F. cinerea Vill., F. drymeia Mert. & W.D.J. Koch, F. elegans Boiss., F. gauthieri (Hack.) K. Richt., F. glauca Vill., F. kasmiriana Stapf, F. mairei St.-Yves, F. muelleri Vickery, F. pallens Host, F. pseudoeskia Boiss., F. rupicaprina (Hack.) A. Kern., F. spectabilisJan, and F. varia Haenke. These species have not become established in the Flora region; only F. amethystina and F. glauca are included in this account. The distribution of some taxa that are grown for turf, revegetation, and, to a lesser extent, horticulture—such as Festuca rubra subsp. rubra, F. trachyphylla, F. filiformis, and F. valesiaca—is continually expanding because of their wide commercial availability. The occurrence of these in the Flora region is no doubt much more extensive than current herbarium collections indicate. The taxonomy of the genus is problematic and contentious, and this treatment is far from definitive. Keying the species ultimately relies on characters that are sometimes difficult to detect on herbarium specimens, such as ovary pubescence and leaf blade sclerenchyma patterns. Because of the intraspecific variability in many characters, combinations of overlapping characters must be employed for identification. The distribution of sclerenchyma tissue within the vegetative shoot leaves is often an important diagnostic character in Festuca. Taxa in a small region can often be identified reliably without resorting to consideration of these patterns but, for the Flora region as a whole, their use is essential. These patterns should be observed in cross sections made from mature, but not senescent, leaves of vegetative shoots, 1/4 to halfway up the blades; they can be made freehand, with a single-edged razor blade. Sections are best viewed at 40× or greater magnification, and with transmitted light (polarized if possible). There are five main sclerenchyma distribution patterns in Festuca. Almost all species have a strand of sclerenchyma tissue along the margins and opposite the midvein against the abaxial epidermis. Strands may be narrow (about as wide as the adjacent veins or narrower) to broad (wider than the adjacent veins). Additional strands are often present at the abaxial surface opposite the veins; these strands may be confluent, sometimes combining to form a cylinder around the leaf and appearing as a continuous ring or band in the cross sections. Some species have additional strands on the adaxial surface opposite some or all of the veins. Another variant is for the abaxial sclerenchyma strands to extend inwards to some or all of the vascular bundles (veins), forming pillars in the cross sections. If both the abaxial and adaxial strands extend inward to the vascular bundles, they are said to form girders. Some of the patterns described may co-occur within a leaf. For instance, some veins may be associated with pillars, others with girders; some sclerenchyma strands within a leaf may be confluent, whereas others are not. Although there may be considerable variation in the extent of sclerenchyma development, the general pattern within a species is usually constant. It is this that makes such patterns useful diagnostic characters, particularly for those needing to identify plants in vegetative condition. They have not, however, been examined for all species. Descriptions of leaf blades are based on the leaves of the basal vegetative shoots, where present. For those without basal tufts of vegetative shoots, the cauline leaves are described. Width measurements are provided for leaves that are usually flat, or almost so, when encountered in the field or herbarium. “Diameter” is given for leaves that are usually folded or conduplicate when encountered; for leaves that are oval in cross section when folded, it is the largest diameter (or width). Closure of the leaf sheaths should be checked on young leaves, because the sheaths often split with age, leading to underestimations of the extent of their closure. The fraction of the leaf sheath that is closed varies within and between species of Festuca, but the species can be divided into three categories in this regard: those such as F. rubra, in which the leaves are closed for at least 3/4 their length; those such as F. saximontana, in which they are closed from 1/3 to slightly more than 1/2 their length; and those such as F. trachyphylla, in which they are not closed or closed for less than 1/4 their length. The descriptions indicate to which of these categories each species belongs. Lemma awns tend to be longer, and should be measured, on the distal florets within a spikelet. Under adverse conditions, many species may proliferate vegetatively, where leafy bulbils or shoots form in place of some or all spikelets. Some populations of Festuca are largely (or completely) sterile, reproducing almost entirely through such bulbils, a process termed pseudovivipary. Pseudoviviparous plants may be common or even abundant in certain areas and habitats. Since these stabilized forms are largely reproductively isolated, often of unusual ploidy, and largely morphologically distinct, they are treated as separate species. Although the lower bracts in pseudoviviparous spikelets are usually more or less normal in form, they are sometimes elongated or distorted, as are the upper bracts. SELECTED REFERENCES Aiken, S.G. and L.L. Consaul. 1995. Leaf cross sections and phytogeography: A potent combination for identifying members of Festucasubgg. Festuca and Leucopoa (Poaceae), occurring in North America. Amer. J. Bot. 82:1287–1299; Aiken, S.G., L.L. Consaul, J.I. Davis and P.S. Manos. 1993. Systematic inferences from variation in isozyme profiles of arctic and alpine cespitose Festuca (Poaceae). Amer. J. Bot. 80:76–82; Aiken, S.G., L.L. Consaul and L.P. Lefkovitch. 1995. Festuca edlundiae (Poaceae), a high arctic, new species compared enzymatically and morphologically with similar Festuca species. Syst. Bot. 20:374–392; Aiken, S.G. and S.J. Darbyshire. 1990. Fescue Grasses of Canada. Agriculture Canada Publ. 1844/E. Canadian Government Publishing Centre, Ottawa, Ontario, Canada. 113 pp.; Aiken, S.G., M.J. Dallwitz, C.L. McJannet and L.L. Consaul. 1997. Biodiversity among Festuca (Poaceae) in North America: Diagnostic evidence from DELTA and clustering programs, and an INTKEY package for interactive, illustrated identification and information retrieval. Canad. J. Bot. 75:1527–1555; Aiken, S.G., S.J. Darbyshire and L.P. Lefkovitch. 1985. Restricted taxonomic value of leaf sections in Canadian narrow-leaved Festuca (Poaceae). Canad. J. Bot. 63:995–1007; Aiken, S.G. and G. Fedak. 1991. Cytotaxonomic observations on North American Festuca (Poaceae). Canad. J. Bot. 70:1940–1944; Aiken, S.G. and S.E. Gardiner. 1991. SDS-PAGE of seed proteins in Festuca (Poaceae): Taxonomic implications. Canad. J. Bot. 69:1425–1432; Aiken, S.G., S.E. Gardiner, and M.B. Forde. 1992. Taxonomic implications of SDS-PAGE analysis of seed proteins in North American taxa of Festuca subgenus Festuca (Poaceae). Biochem. Syst. & Ecol. 20:615–629; Aiken, S.G. and L.P. Lefkovitch. 1984. The taxonomic value of using epidermal characteristics in the Canadian rough fescue complex (Festuca altaica, F. campestris, F. hallii, “F. scabrella”). Canad. J. Bot. 62:1864–1870; Aiken, S.G. and L.P. Lefkovitch. 1993. On the separation of two species within Festuca subg. Obtusae (Poaceae). Taxon 42:323–337; Alexeev, E.B. 1977. To the systematics of Asian fescues (Festuca): I. Subgenera Drymanthele, Subulatae, Schedonorus, Leucopoa. Byull. Moskovsk. Obshch. Isp. Prir., Otd. Biol., n.s., 82(3):95–102. [In Russian]; Alexeev, E.B. 1980. Festuca L.: Subgenera et sectiones novae ex America boreali et Mexico. Novosti Sist. Vyssh. Rast. 17:42–53. [In Russian]; Alexeev, E.B. 1982. New and little known fescues (Festuca L.) of North America. Byull. Moskovsk. Obshch. Isp. Prir., Otd. Biol., n.s., 87(2):109–118. [In Russian]; Alexeev, E.B. 1985. Festuca L. (Poaceae) in Alaska et Canada. Novosti Sist. Vyssh. Rast. 22:5–35. [In Russian]; Auquier, P. 1971. Festuca rubra subsp. pruinosa (Hack.) Piper: Morphologie, écologie, taxonomie. Lejeunia, n.s., 56:1–16; Barker, C.M. and C.A. Stace. 1982. Hybridization in the genera Vulpia and Festuca: The production of artificial F1 plants. Nordic J. Bot. 2:435–444; Beal, W.J. 1896. Grasses of North America, vol. 2. Henry Holt & Company, New York, New York, U.S.A. 706 pp.; Catalán, P., P. Torrecilla, J.A. López Rodrı́guez and Richard G Olmstead. 2003. Phylogeny of the festucoid grasses of subtribe Loliinaeand allies (Poeae, Pooideae) inferred from ITS and trn L–F sequences. Molecular Phylogenetics and Evolution 31:517-541 [ |
