page_title: Vavilovian mimicry
section_title: Examples
hierarchical_section_title: Vavilovian mimicry / Examples
caption_attribution_description: Secale cereale Polski: Żyto zwyczajne English: Rye Русский: Ржаное поле.
context_page_description: In plant biology, Vavilovian mimicry is a form of mimicry in plants where a weed comes to share one or more characteristics with a domesticated plant through generations of artificial selection. It is named after Nikolai Vavilov, a prominent Russian plant geneticist. Selection against the weed may occur by killing a young or adult weed, separating its seeds from those of the crop, or both. This has been done manually since Neolithic times, and in more recent years by agricultural machinery.
  Vavilovian mimicry is a good illustration of unintentional selection by humans. Although the human selective agents might be conscious of their impact on the local weed gene pool, such effects go against the goals of those growing crops. Weeders do not want to select for weeds that are increasingly similar to the cultivated plant, yet the only other option is to let the weeds grow and compete with crops for sunlight and nutrients. Similar situations include antibiotic resistance and, of similar nature to crop mimicry, herbicide resistance. This can be contrasted with other forms of artificial selection that do tend toward a favorable outcome, such as selective breeding.
context_section_description: One case of Vavilovian mimicry is the gold-of-pleasure or false flax (Camelina sativa linicola), which looks much like the flax plant Linum usitatissimum, and occurs with it in the field. The gold-of-pleasure is a descendant of Camelina gabrata, a wild species; its subspecific name linicola means "the one that lives with flax". Weeding of the adult plant is impractical; instead they are separated based on properties of the seed. This is done by a winnowing machine, which in this case acts as an inanimate signal receiver. Seeds that are thrown the same distance as flax seeds have thus been selected for, making it near impossible to separate the seeds of these two species.
  Another example is rye (Secale cereale), a grass which is derived from wild rye (Secale montanum), a widely distributed Mediterranean species. Rye was originally just a weed growing with wheat and barley, but came under similar selective pressures to the crops. Like wheat, it came to have larger seeds and more rigid spindles to which the seeds are attached. However, wheat is an annual plant, while wild rye is a perennial. At the end of each growing season wheat produces seeds, while wild rye does not and is thus destroyed as the post-harvest soil is tilled. However, there are occasional mutants that do set seed. These have been protected from destruction, and rye has thus evolved to become an annual plant.
  Rye is a hardier plant than wheat, surviving in harsher conditions. Having become preadapted as a crop through wheat mimicry, rye was then positioned to become a cultivated plant in areas where soil and climatic conditions favored its production, such as mountainous terrain.
  This fate is shared by oats (Avena), which also tolerate poorer conditions, and like rye, grow as a weed alongside wheat and barley. Derived from a wild species (Avena sterilis), it has thus come to be a crop in its own right. Once again paralleling wheat, rye and other cereals, oats have developed tough spindles which prevent seeds from easily dropping off, and other characters which also help in natural dispersal have become vestigial, including the awns which allow them to self bury.
  The flax-dodder (Cuscuta epilinum) is a creeper that grows around flax and linseed plants. Much like the other cases, its seeds have become larger. A mutant double-seeded variety has become prevalent, as seed size has once again been the character upon which selection has acted.
  Selection can also occur on the vegetative stage, through hand weeding. Weeding often takes place when the crop plant is very young, and most vulnerable. Echinochloa oryzoides, a species of grass which is found as a weed in rice (Oryza sativa) fields, looks similar to rice and its seeds are often mixed in rice and difficult to separate. This close similarity was enhanced by the weeding process which is a selective force that increases the similarity of the weed in each subsequent generation.
caption: Rye is a secondary crop, originally being a mimetic weed of wheat.
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