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Being compiled by M.E. Barkworth, to whom corrections and suggestions should be sent.]; Topics: Circumscription, distribution, size, cytogenetics, list of species

Circumscription: Elymus is interpreted here as comprising primarily caespitose, short-anthered species with non-disarticulating rachises, and lanceolate, somewhat flexible, glumes and their genetically close relatives. The last phrase brings into Elymus a few rhizomatous, long-anthered species (e.g., Elymus repens, E. lanceolatus), some species with almost no glumes (e.g., E. hystrix), and some with disarticulating rachises as well as narrow, awn-like glumes (e.g., E. elymoides).

The number of spikelets at each node is not important; it may be 1 (as in sect. Roegneria and many of the species that used to be placed in Agropyron) or more than 1 (as in E. viriginicus, E. canadensis, etc.).

For different viewpoints on the circumscription of Elymus, see Assadi and Runemark (1995) (who interpret it to include Thinopyrum and Pseudoroegneria plus many other segregates) or Baum et al. (1991) (who treat Roegneria and Elytrigia as distinct genera). For a revision of the South American taxa, see Seberg and Petersen (1998).

Distribution: Elymus is a cool-temperate genus. It is most abundant in Asia and North America, but extends into Europe, South America, and Australia.

Size: Elymus probably consists of around 200 species. Estimating its size is difficult because its greatest diversity is in Asia, many parts of which are poorly known botanically speaking. An additional complication is a consequence of the differing species interpretations that have been adopted. North American species are thought to have low barriers to interspecific hybridization. Interestingly, this does not seem to be true of Asian species (von Bothmer, pers. comm).

Genomic composition: Elymus is an alloploid genus, all of whose members (so far as is known) possess the St genome in combination with at least one other genome. Most species are tetraploids, but there are many hexaploids and possible some octoploids. All native North American species examined are tetraploids in which the second genome is the H genome. Many Asian species are also tetraploids, but with the Y genome as the additional genome. Other genomes known to occur in Elymus are the P and E genomes.

Table of species: The following table will be built up very slowly (unless funding becomes available). The synonyms listed are those that seem to be in recent or current use and are provided to help in interpretation of the treatment reflected by the first column. Genomic information is provided ONLY if it has been obtained via investigation of the species involved. Reports that do not list voucher specimens made at the time of the genomic investigation are asterisked. They should be repeated, with vouchers being deposited in a herbarium that regularly makes loans available. The species are listed alphabetically for now. The links below will aid in locating names in the first column.

E. abolinii var. pluriflorus D.F. Cui   China (Xinjiang)
E. alaskanus      
E. alaskanus subsp. islandicus (Melderis) A. Love & D. Love      
E. alaskanus subsp. subalpinus (Neuman) A. Love & D. Love      
Elymus alopex B. Salomon   Iceland  
E. altaicus D.F. Cui   China (Xinjiang)  
E. angulatus J. Presl in C. Presl Agropyron breviaristus Hitchc. Peru south to Tierra del Fuego, east to western Argentina and Bolivia 2n=28
E. anthosachnoides (Keng) A. Löve R. anthosachnoides Keng Southwestern China (Sichuan, Yunnan). [Lu 1993] StY
E. cacuminus B.-R. Lu & B. Salomon   Western China (Sichuan), Nepal, Sikkim, Tibet. [Lu 1993] StY
E. canaliculatus (Nevski) Tzvelev Agropyron canaliculatum Nevski; Roegneria canaliculata (Nevski) Ohwi; Elymus longearistatus subsp. canaliculatus (Nevski) Tzvelev; A. longearistatum var. aitchisonii Boissier Alai, Iran, Kashmir, Pakistan (Gilgit, NWFP), Pamir, Tadzhikistan, Tibet. [Lu 1993] StY
E. caninus (L.) L.      
E. caninus var. behmii (Melderis) Jaaska      
E. caninus (L.) L.var. caninus      
E. caninus var. donianus (F.B. Whie) Jaaska      
E. caninus var. muticus (Holm.) T. Karlsson      
E. caucasicus (C. Koch) Tzvelev Roegneria caucasicus C. Koch; Agropyron caucasicum (C. Koch) Grossh.; Agropyron roegneri (Griseb.) Boissier; R. linczevskii Czopan. Daghestan, Turkmenia, northern Iran. [Lu 1993] StY
E. ciliaris (Trin.) Tzvelev     StY
E. cordilleranus Davidse & R.W. Pohl Costa Rica, south through the Andes to Peru and Bolivia 2n=28  
E. elymoides (Raf.) Swezey Sitanion hystrix Western North America StH
E. elymoides subsp. brevifolius (J.G. Smith) Barkworth Sitanion brevifolius J.G. Smith Western North America StH
E. elymoides subsp. californicus Sitanion californicum J.G. Smith Western North America StH
E. elymoides subsp. elymoides Western North America StH
E. elymoides subsp. hordeoides Sitanion hordeoides Suksdorf Western North America; rare StH
E. dahuricus Turcz. ex Griseb.     StYH
E. fibrosus (Schrenk) Tzvelev      
E. formosanus (Honda) A. Löve Agropyron formosanum Honda; Roegneria formosana (Honda) Ohwi; R. formosana var. longearistata Keng; R. formosana var. pubigera Keng Formosa Island. [Lu 1993]] ?
E. glaberrimus var. breviaristatus D.F. Cui China (Xinjiang)  
E. glaucescens Seberg Agropyron pubiflorum (Steudel) Parodi; A. antarcticum Parodi Southern Chile and Argentina 2n=28
E. gmelinii (Ledeb.) Tzvelev   Central and East Asia, StY
E. humidus (Ohwi & Sakamoto) Osada     StYH
 E. jacquemontii (Hooker f.) Tzvelev Agropyron jacquemontii Hooker f; Roegneria jacquemontii (Hooker f.) Nevski; Anthosachne jacquemontii (Hooker f.) Nevski  Western Tibet and the Himalayas, above 3900 m. [Lu 1993]  StY
E. kaschgaricus D.F. Cui China (Xinjiang)  
E. longearistatus (Boissier) Tzvelev Agropyron longearistatum (Boissier) Boissier; Anthosachne longearistata (Boissier) Nevski; Roegneria longearistata (Boissier) Drobov; A. longearistata var. haussknechtii Boissier Gissar-Darvaz, Iran, Tadzhikistan. [Lu 1993] StY
E. magnicaespes D.F. Cui China (Xinjiang)  
E. mendocinus (Parodi) A. Love Agropyron mendocinum Parodi Argentina (endemic around Mendoza) 2n=56
E. mutabilis Drobov) Tzvelev    
E. mutabilis var. nemoralis S.L. Chen ex D.F. Cui China (Xinjiang)  
E. nipponicus Jaaska   StY  
E. parodii Seberg & G. Petersen A. condensatum J. Presl Southern Brazil, Uruguay, and northern Argentina 2n=28
E. patagonicus Speg.   Southern Argentina and Tierra del Fuegao 2n-42
E. repens (L.) Gould Cosmopolitan weedy species  
Elytrigia repens subsp. longearistata N.R. Cui China (Xinjiang)  
Elytrigia repens var. subulatum Seberg & G. Petersen  
E. retroflexus B.-R. Lu & B. Salomon Tibet [Lu 1993] StY
E. x russellii (Melderis) Cope Agropyron russellii Melderis Pakistan (near Makerum, Hispar, and Biafo glaciers). [Lu 1993] ?
E. scabriglumis (Hackel) A. Love Argentina and Chile 2n=28
 E. schugnanicus (Nevski) Tzvelev Agropyron schuganicum Nevski; Roegneria schugnanica (Nevski) Nevski Gissar-Darvaz, Pamir and, reportedly, northeastern Iran andwestern Himalayas. [Lu 1993] ?
E. semicostatus (Steud.) Melderis Triticum semicostatum (Nees ex Steud.; Roegneria semicostata (Sted.) Kitag.   StY (Svitashev et al. 1998)
E. serotinous (Keng) A.Löve R. serotina Keng Central China (Shaanxi). [Lu 1993] ?
Elymus sibiricus L.  
E. sinkiangensis D.F. Cui China (Xinjiang)  
E. stebbinsii Gould Agropyron parishii Scribner   J.G. Smith California (See Barkworth 1997)  
E. stebbinsii subsp. septentrionalis Barkworth California (See Barkworth 1997)    
E. tschimganicus var. glabrispiculus D.F. Cui China (Xinjiang)    
E. tsukushiensis Honda     StYH
Elymus wawawaiensis J.R. Carlson & Barkworth StH    
 E. yangiiB.-R. Lu Western China and Tibet, between 3-4200 m [Lu 1993]    StY
E. yubaridakensis (Honda) Ohwi   Japan  
Elymus antiquus (Nevski) Tzvelev  Agropyron antiquus Nevski; A. microlepis Bor; Roegneria parvigluma Keng Western and northwestern China (Qinghai, Sichuan, Yunnan), Nepal, and Tibet. [Lu 1993] StY
 Elymus brevipes (Keng) A. Löve Roegneria brevipes Keng Western and northwestern China (Gansu, Qinghai, Sichuan), and Tibet. [Lu 1993] StY
 Elymus burchan-buddae (Nevski) Tzvelev)  Agropyron burchan-buddae Nevski; A. nutans Keng; A. breviglume Keng, Roegneria breviglumis (Keng) Keng  Western and northwestern China (Gansu, Qinghai, Sichuan, Xinjiang, Yunnan), and Tibet. Probably also in Nepal and northern India. [Lu 1993] StY
 Elymus sclerus A. Löve  Roegneria dura (Keng) Keng  Western and northwestern China (Gansu, Qinghai, Sichuan, Xinjiang), and Tibet. [[Lu 1993]  StY
E. alaskanus (Scribner & Merr.) A. Löve  
E. alaskanus (Scribner &Merr.) A. Löve subsp. alaskanus Agropyron boreale (Turcz.) Drobow; Roegneria borealis (Turcz.) Nevski Elymus kronokensis subsp. borealis (Turcz.) Tzvelev Alaska, Canada (Yukon, Northwest Territories)  
E. alaskanus subsp. latiglumis (Scribner & J.G. Sm.) A. Löve Agropyron latiglume (Scribner & J.G. Sm.) Rydb.; A. caninum var. latiglume (Scribner & J.G. Sm.) Pease & A.H. Moore; Elymus trachycaulus var. latiglume (Scribner & J.G. Sm.) Beetle; A. violaceum (Hornem.) Lange; R. violacea (Hornem.) Melderis Canada (Alberta, BC) USA (Alaska, Idaho, Washington, Montana, Wyoming)  
E. hyperarcticus (Polunin) Tzvelev Agropyron boreale var. hyperarcticum (Polunin) A. Löve & D. Löve; Roegneria borealis subsp. hyperarctica (Polunin) A. Löve & D. Löve; Elymus hyperarcticus (Polunin) Tzvelev; E. sajanensis subsp. hyperarcticus (Polunin) Tzvelev; E. alaskanus subsp. hyperarcticus (Polunin) A. Löve & D. Löve USA (Alaska); Russia (Arctic)  
E. californicus (Bolander ex Thurber) Gould Hystrix californica Bolander ex Thurber [Molecular data suggest that it belongs in Leymus]  USA (California, around San Francisco Bay). 56
E. transhyrcanus (Nevski) Tzvelev Roegneria transhyranicus Nevski; Agropyron transhyranicum (Nevski) Bondartseva; Roegneria leptoura Nevski; Semiostachys leptoura (Nevski) Drobov; Elytrigia vvedenskyi Drobov Iran and central Asia StStH