![Brassicaceae spp Sturm30](https://upload.wikimedia.org/wikipedia/commons/b/b5/Brassicaceae_spp_Sturm30.jpg)
In plant biology, Vavilovian mimicry (also crop mimicry or weed mimicry) is a form of
mimicry in plants where a
weed
A weed is a plant considered undesirable in a particular situation, "a plant in the wrong place", or a plant growing where it is not wanted.Harlan, J. R., & deWet, J. M. (1965). Some thoughts about weeds. ''Economic botany'', ''19''(1), 16-24. ...
evolves to share one or more characteristics with a
domesticated plant
Domestication is a sustained multi-generational relationship in which humans assume a significant degree of control over the reproduction and care of another group of organisms to secure a more predictable supply of resources from that group. A ...
through generations of
artificial selection.
It is named after
Nikolai Vavilov
Nikolai Ivanovich Vavilov ( rus, Никола́й Ива́нович Вави́лов, p=nʲɪkɐˈlaj ɪˈvanəvʲɪtɕ vɐˈvʲiləf, a=Ru-Nikolay_Ivanovich_Vavilov.ogg; – 26 January 1943) was a Russian and Soviet agronomist, botanist ...
, a prominent Russian
plant
Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclu ...
geneticist
A geneticist is a biologist or physician who studies genetics, the science of genes, heredity, and variation of organisms. A geneticist can be employed as a scientist or a lecturer. Geneticists may perform general research on genetic processes ...
.
Selection against the weed may occur by killing a young or adult weed, separating its seeds from those of the crop (
winnowing
Winnowing is a process by which chaff is separated from grain. It can also be used to remove pests from stored grain. Winnowing usually follows threshing in grain preparation. In its simplest form, it involves throwing the mixture into the ...
), or both. This has been done manually since
Neolithic
The Neolithic period, or New Stone Age, is an Old World archaeological period and the final division of the Stone Age. It saw the Neolithic Revolution, a wide-ranging set of developments that appear to have arisen independently in several p ...
times, and in more recent years by
agricultural machinery
Agricultural machinery relates to the mechanical structures and devices used in farming or other agriculture. There are many types of such equipment, from hand tools and power tools to tractors and the countless kinds of farm implements that ...
.
Vavilovian mimicry is a good illustration of unintentional
selection
Selection may refer to:
Science
* Selection (biology), also called natural selection, selection in evolution
** Sex selection, in genetics
** Mate selection, in mating
** Sexual selection in humans, in human sexuality
** Human mating strateg ...
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
Competition is a rivalry where two or more parties strive for a common goal which cannot be shared: where one's gain is the other's loss (an example of which is a zero-sum game). Competition can arise between entities such as organisms, indivi ...
with crops for
sunlight and
nutrients
A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excre ...
. Similar situations include
antibiotic resistance and, also in agricultural crops,
herbicide resistance. Having acquired many desirable qualities by being subjected to similar selective pressures, Vavilovian mimics may eventually be domesticated themselves. Vavilov called these weeds-become-crops secondary crops.
Classification and comparisons
Vavilovian mimicry can be classified as reproductive,
aggressive
Aggression is overt or covert, often harmful, social interaction with the intention of inflicting damage or other harm upon another individual; although it can be channeled into creative and practical outlets for some. It may occur either reacti ...
(
parasitic
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...
) and, in the case of secondary crops, mutualistic. It is a form of ''disjunct'' mimicry with the model agreeable to the dupe.
In disjunct mimicry complexes, three different species are involved as model, mimic and dupe—the weed, mimicking a protected crop model, with humans as signal receivers. Vavilovian mimicry bears considerable similarity to
Batesian mimicry (where a harmless organism mimics a harmful species) in that the weed does not share the properties that give the model its protection, and both the model and the dupe (in this case humans) are negatively affected by it. There are some key differences, though; in Batesian mimicry the model and signal receiver are enemies (the
predator
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...
would eat the protected species if it could), whereas here the crop and its human growers are in a
mutualistic relationship: the crop benefits from being dispersed and protected by people, despite being eaten by them. In fact, the crop's only 'protection' relevant here is its usefulness to humans. Secondly, the weed is not eaten, but simply killed (either directly or by not planting the seed). The only motivation for killing the weed is its effect on crop yields. Farmers would prefer to have no weeds at all, but a predator would die if it had no prey to eat, even if they might be difficult to identify. Finally, there is no known equivalent of Vavilovian mimicry in ecosystems unaltered by humans.
Delbert Wiens has argued that secondary crops cannot be classified as mimics, because they result from artificial as opposed to
natural selection
Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations. Cha ...
, and because the selective agent is a
machine. On this first point, Georges Pasteur points out that "indirect artificial selection" is involuntary and thus no different from natural selection.
That the signal receiver is an inanimate object certainly deviates from the normal case of a dupe
perceiving the signal, but the result is no different from that of manual selection that has been occurring since the
Neolithic Revolution.
Examples
![Secale cereale](https://upload.wikimedia.org/wikipedia/commons/a/a6/Secale_cereale.jpg)
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
In zoological nomenclature, a subspecific name is the third part of a trinomen. In zoology there is only one rank below that of species, namely "subspecies".
In botanical nomenclature, there are several levels of subspecific names, such as ''var ...
''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
A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiospe ...
. This is done by a
winnowing machine
Winnowing is a process by which chaff is separated from grain. It can also be used to remove pests from stored grain. Winnowing usually follows threshing in grain preparation. In its simplest form, it involves throwing the mixture into t ...
, 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.
![Avena-sativa](https://upload.wikimedia.org/wikipedia/commons/4/4d/Avena-sativa.jpg)
Another example is
rye (''Secale cereale''), a
grass
Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns a ...
which is derived from wild rye (''
Secale montanum''), a widely distributed Mediterranean species. Rye was originally just a weed growing with
wheat
Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat (''T. aestivum''). The archaeologi ...
and
barley
Barley (''Hordeum vulgare''), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains, particularly in Eurasia as early as 10,000 years ago. Globally 70% of barley p ...
, 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
A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also wid ...
. 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
mutant
In biology, and especially in genetics, a mutant is an organism or a new genetic character arising or resulting from an instance of mutation, which is generally an alteration of the DNA sequence of the genome or chromosome of an organism. It ...
s 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
The oat (''Avena sativa''), sometimes called the common oat, is a species of cereal grain grown for its seed, which is known by the same name (usually in the plural, unlike other cereals and pseudocereals). While oats are suitable for human co ...
(''Avena sativa'' and ''
Avena byzantina''), which also tolerate poorer conditions, and like rye, grow as a weed alongside wheat and barley. Derived from a wild species (''
Avena sterilis
''Avena sterilis'' (animated oat, sterile oat, wild oat, wild red oat, winter wild oat; syn. ''Avena ludoviciana'' Durieu; ''Avena sterilis'' ssp. ''ludoviciana'' (Durieu) Gillet & Magne in ''Federal Noxious Weed Disseminules of the U.S.'') is a ...
''), 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 characteristics which also help in natural
dispersal have become
vestigial
Vestigiality is the retention, during the process of evolution, of genetically determined structures or attributes that have lost some or all of the ancestral function in a given species. Assessment of the vestigiality must generally rely on co ...
, including the
awns which allow them to self bury.
The flax-dodder (''
Cuscuta epilinum
''Cuscuta epilinum'' is a species of flowering plant belonging to the family Convolvulaceae.
Its native range is Iran to Central Asia.
References
Cuscuta, epilinum
{{Botany-stub ...
'') 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
Rice is the seed of the grass species '' Oryza sativa'' (Asian rice) or less commonly ''Oryza glaberrima'' (African rice). The name wild rice is usually used for species of the genera '' Zizania'' and '' Porteresia'', both wild and domesticat ...
(''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.
See also
*
Threshing
Threshing, or thrashing, is the process of loosening the edible part of grain (or other crop) from the straw to which it is attached. It is the step in grain preparation after reaping. Threshing does not remove the bran from the grain.
History ...
Notes
References
Sources
* One of the most extensive articles on the topic.
* Discussion of crop mimicry among many other plant cases.
* A significant portion discusses weeds.
*
Further reading
*
*
{{DEFAULTSORT:Vavilovian Mimicry
Mimicry
History of agriculture