Imitation

The imitation is adaptive strategy of imitation. This makes it possible for example a species to escape possible predator. The strategies imitations are various types as the species which have means of escaping the vision from the predator, one speaks then about camouflage or imitation cryptic, or like the fact of being made pass for another species, for example by avoiding attributes of nonedible species, even dangerous. However, the imitation can answer other constraints, the such reproduction (case of the cuckoos or some Orchidée S) or the predation (case of the blénnie devourer).

There exists a major difference between the imitation with the camouflage from the point of view in their evolution: if the aptitude for the camouflage, in particular by the color, can appear and develop very quickly within a species by the play of the changes and the selection (example of the moth of the birch), the imitation on the contrary implies a complex mechanism of Co-evolution bringing into play three species: the MIME, the imitated species and the deceived species. The Homochromie is the imitation of the colors and the Homotypie is the imitation of the forms.

Discovered historical

It is the British entomologist Henry Walter Bates (1825-1892), naturalist and explorer who spent eleven years to Amazonia, which theorizes the first time on the imitation in connection with similar butterflies of aspects although not being close species, an inoffensive species benefitting from the repulsion caused by a poisonous species. It created the English word " then; mimicry" , a neologism worked on the Greek and who means " capacity with mimer". Fritz Müller (1834-1895), a Swiss zoologist, explains for the first time in 1878, the phenomenon according to which two different poisonous species will adopt the same appearance by the improvement of the effectiveness of their delivered. Their predator more quickly learning how to be wary of them. It is in their honor that the two types of imitation are named: the imitation batesien and the imitation mullérien.

Three actors of the imitation

• the model, transmitter of stimuli or signals perceptible by the directions, in other words the species reference.

• the MIME, that which imitates the species reference, animal or plant, and which draw advantage from its resemblance to the model.
• deceives It, very often a Prédateur, whose directions (for example sight) perceive same manner the stimulis emitted by the model and the MIME. It is called also " opérateur" because the selective pressure is exerted through him: it is the actor of the evolution of the imitation.

Forms of imitation

The Batésien imitation

The theory of Henry Walter Bates is founded on the training of the predator. This one, after a certain number of experiments, learned how to know the species which will be used as model to the MIME, and adopts the same behavior with regard to the MIME. The Batésien imitation also consists of the imitation, by a species deprived of means of defense, of a species equipped better from this point of view there. One notices in particular butterfly monarch, of which Caterpillars nourish plants toxic and of this fact adults are also toxic, which encourages the predatory ones which already made the bad experiment eat one of them, not to renew it. Thus many other butterflies (for example the butterfly viceroy) will imitate the colors and the drawing of the wings of the monarch to profit from this effective protection. One distinguishes thus from many mimetic flies (like the éristale), or from the species underwater, like the blennie devourer, which imitates in any point the cleaning labre (small fish which nourishes parasites of other fish that it collects on their body or in their mouth), and thus will approach closest to his preys for better devouring them. The imitation is in this aggressive case as well as defensive.

The Mullérien imitation

It consists of a reciprocal imitation within a group of nonedible species or simply unpleasant (vomitory for example), include/understand possibly a really dangerous species. Here, the training of the predator is accelerated by the resemblance (he learns how to avoid the preys which resembles each other). It is a form of evolutionary Convergence.

The Mertensien imitation

Thus named according to the Herpétologiste (scientific studying the reptiles) German Robert Mertens (1894-1975), it however relates to models equipped with specific signals it is the species mortal which imitates the least dangerous species.

Car-imitation

The car-imitation is the case of animals imitating a portion only body of a predator or of their own body. For example, of many butterflies and fresh water fish species have " spots simulating a eye ". They are intended to create the surprise on the predator and to give to the prey time to flee. Moreover it can, of share the orientation of the signal to mislead perceptions of the predatory ones. It is the case of the snakes called “to two heads”, such as for example the False-coral Anilius scytale , which, when it is driven back righting its tail in height and the balance, dissimulating its head.

Camouflage

The camouflage is a different step since it consists in imitating inanimate objects of the environment like a stone (case of the fish hones), a sheet, a brushwood (case of the phasmes Phasme S), droppings… the largest species do not imitate a particular object but a tone, thus the dresses mottled of the leopards are based in the bush. The dress of the Zèbre S is particularly adapted to the visual system of its most dangerous predator, the lion. Two types of camouflage can coexist the Homochromie is the imitation of the colors and the Homotypie is the imitation of the forms.

Some species of the wet tropical forests developed a capacity to change their color to be melted with their environment. This strategy can be as well aggressive as defensive. It is the case for example Caméléon S or geckos Uroplatus of Madagascar. They lay out of cells of the skin called Chromatophore S which are capable of this change of coloring known as enigmatic.

Mimetic strategies

Many forms of life exploit a morphological resemblance to an element of their natural environment to be melted there. By its forms, colors, odors and savors, or its, the MIME resembles as much as possible a target which presents:

• a nutritive interest limited for the predator: the Phasme with the appearance of a brushwood which an insectivorous bird will scorn, the octopus is made invisible while merging with sea-bed, while imitating its color and its texture;
• a potential danger for the predator: certain flies resemble to mistake there with wasps, certain snakes deprived of venom imitate the aural signal of the Crotale, several species of butterflies have reasons on their wings which resemble the eyes of an animal much larger than them;
• a gustatory or nutritive interest important for the fertilizer: certain plants benefit from the interest of the insects for another species for their own reproduction;

• a nutritive interest for their prey: plants carnivores exhale a perfume of flesh in putrefaction to attract flies of which they are nourished;
• a danger limited for their prey: certain fish have a camouflage with the colors of the algae in which they evolve/move to surprise their meal.
• an ideal admitted by congeneric, making possible certain behaviors: the ants imitate their respective odors by permanent exchange, which builds the odor characteristic of their colony, which will enable them to enter there.

External bonds

• Examples of imitation in the animal world

• Warning Color and Mimicry Reading outline from University College London
• Camouflage and Mimicry in Fossils
• Chemical Mimicry in Pollination

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