''Elymus caninus'', the bearded couch or bearded wheatgrass, is a species of

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...

in the family

Poaceae Poaceae ( ), also called Gramineae ( ), is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos, the grasses of natural grassland and species cultivate ...

that is native to Europe including the UK but can be found introduced in the US states of

Oregon Oregon ( , ) is a U.S. state, state in the Pacific Northwest region of the United States. It is a part of the Western U.S., with the Columbia River delineating much of Oregon's northern boundary with Washington (state), Washington, while t ...

and

Washington Washington most commonly refers to: * George Washington (1732–1799), the first president of the United States * Washington (state), a state in the Pacific Northwest of the United States * Washington, D.C., the capital of the United States ** A ...

. ''E. caninus'' has been observed in two morphotypes; the first population being "pauciflorum," with the second being "caninus." Found in the forest regions throughout Europe and stretching as far as west Asia, ''Elymus caninus'' is a type of self-pollinating wheatgrass. It is described as green, lax-leafed, and caespitose. The widespread distribution of ''E. caninus'' has led to sizable differences in morphology, isozyme, prolamine, and DNA levels. Morphological differences seen throughout ''E. caninus'' populations include: the number of florets per spikelet, the length of lemma awn, and the pubescence of leaves and their sheaths. Populations from China, Italy, Pakistan, and Russia were determined to have the lowest levels of intra-population variation among ''E. caninus'' morphologies. These lower levels may be due to selection factors, population bottlenecks, genetic drift, or a combination of the bunch. While generally a self-pollinating perennial, the rate of outcrossing varies among ''Elymus caninus'' populations. This outcrossing occurs when the species florets are open during anthesis. Researchers determined that when ''E. caninus'' is grown near or among other ''Elymus'' species (specifically studied were ''E. mutabilis'' and ''E. fibrosus''), hybridization occurred and these hybrids were mainly found to be sterile. Populations of ''E. caninus'' grown among other ''Elymus'' species showed higher levels of variation when compared to populations grown alone. This finding shows that gene flow may be occurring between the ''Elymus'' species’ and that the gene flow is one-sided (''E. mutabilis'' to ''E. caninus''). Backing up the one-sided gene flow into ''Elymus caninus'', an introgression study of ''Triticum aestivum'' into ''E. caninus'' populations was performed in order to determine if a hybridization would occur in which no spontaneous hybridizations were shown. This concludes that an introgression of the ''T. aestivum'' traits into the ''E. caninus'' population were improbable, disregarding the fact that these populations tend to grow in the same vicinity. Being an allotetraploid, ''E. caninus'' derives its genome (StStHH) from both new and old world ''Pseudoroegneria'' (St) as well as from the small-seeded ''Hordeum'' (H) species. A study completed in 1999 concluded that the fixed heterozygosity without segregation leads to the conclusion that ''E. caninus'' is allotetraploid by nature. A fixed heterozygosity occurs when the diploid parental genomes are homozygous for different alleles, and this trait has been reported in other ''Elymus'' species.

References

caninus Taxa named by Carl Linnaeus {{Pooideae-stub