mimicry
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Mimicry (f.) Describes in biology a form of imitation of visual , auditory or olfactory signals, which leads to the fact that the imitator and forger derives advantages through the deception of the signal receiver. From the point of view of the signal forger, a distinction can be made between two common variants of mimicry: On the one hand, protective mimicry by imitating role models, which for example scare off potential predators; on the other hand, lock mimicry through the imitation of models that are attractive to potential prey or pollinators , for example .
A well-known example of mimicry is the similarity of the shape and color pattern of the petals of certain orchids of the genus Ophrys and certain insects , which is so striking that it gave it its name ( bee ragwort , bumblebee ragwort , fly ragwort ). The flowers of the great spider ragwort imitate the attracting pheromone of female sand bees of the species Andrena nigroaenea - an irresistible lure for the swarming drones to land on these orchid flowers and pollinate them in search of the female.
How these and further into the area of molecular biology sound to differentiate into extensive variations of mimicry and each designate are, is among the researchers discussed controversially; some scientists suggest limiting the term mimicry to Bates' mimicry .
Word origin
The term mimicry is derived from English mimicry (= "imitation"), which in turn is derived from to mimic : "imitate, mimic" + suffix -ry (corresponding to German "-erei") and borrowed from ancient Greek μίμος mímos imitator , Actor.
Principle: signal forgery
Every mimicry system consists of a model, a mimic (mimet) and a signal receiver, which reacts in approximately the same way to the model and the imitator. Such a mimicry system, through its specific shapes, colors or smells, causes the signal receiver to be deceived, to which a “falsified” signal is sent, which the signal receiver interprets either as temptation, as a danger or as irrelevant to it. In the context of evolutionary theory, these analogical patterns, which emerged in the course of tribal history , have the "biological benefit" of increasing the chances of survival of the mimetics and thus the probability of their genes being passed on to the next generation. As for the emergence of all species, Charles Darwin also assumed with regard to mimicry systems that the imitation of models gradually emerged through the selective reinforcement of corresponding mutations .
The problem of the exact classification
It is not always possible to make a clear distinction between mimicry and mimeticism ; an example of this is the African devil flower (Idolomantis diabolicum) , a catching insect , whose front body, equipped with leaf-shaped tentacles, resembles a flower. While many insect species only fly to this "flower" as a supposedly harmless resting place for them (mimicry), other species are attracted by their supposed feeding place (Peckham's mimicry) - and eaten. This distinction makes it clear that the type of interpretation of the signal is significantly influenced by the respective receiver if the signal as a mimetic or mimic classified is. The demarcation to camouflage is also fluid.
Bates' mimicry
Bates' mimicry is the best known form of mimicry. It was scientifically described for the first time in 1862 by Henry Walter Bates in the Transactions of the Linnean Society in London , after he had wandered around in the " primeval forests " of the Brazilian Amazon between 1849 and 1860 and there a. a. had researched the butterfly species . Bates called the imitation of a defensive or inedible animal by harmless animals to deceive enemies as mimicry. It is now known that this is a special case of protective mimicry that was named after the discoverer.
Bates was well aware of the far-reaching evolutionary consequences of his discovery, for he wrote as early as 1862:
"The process by which a mimetic analogy is brought about in nature is a problem which involves that of the origin of all species and all adaptations"
"The process by which the mimetic analogy is brought about in nature is a problem linked to the [problem] of the emergence of all kinds and all adaptations."
Historical
In 1844 a booklet was published anonymously by Robert Chambers under the title "Vestiges of natural history of creation" in England , which caused a stir for years because it contained a number of theories about the origin of the world and animals. The brochure became known in Germany under the title “Natural History of Creation”.
The young British zoologist Alfred Russel Wallace became interested in this brochure and began to think about the origin of the species. He met the British entomologist Henry Walter Bates, who was also very pleased with this brochure. Wallace suggested that Bates take a trip to South America together . Both pursued an ambitious goal, because they wanted to collect facts about the origin of the species in the tropics . There the two came up with the idea of the principle of natural selection (selection) independently of Darwin .
While Wallace only three years in the Amazon - Rainforest remained in Brazil and then in the Malay Archipelago moved on, collected Bates eleven years there animals and plants. He had a very large collection with many completely unknown species, but unlike many previous travelers, Bates was already a real naturalist who not only tracked down rare animals, but also observed the interactions between different animal species and their behavior . When sorting his extensive butterfly collection, he found time and again that the brightly colored noble butterflies contained individual specimens that were very rare and belonged to a completely different family, the white butterflies .
The similarity between these two species was so great that as living moths they were practically indistinguishable from one another. Bates once mentioned: “ I have never succeeded in distinguishing the Leptalis species from species similar to them. "
About Bates' discovery
The genus Dismorphia , formerly Leptalis , forms a number of different species . These species resemble extremely different Ithomiini species.
Dismorphia belongs to the family of the white flies (Pieridae). It is very noticeable that Dismorphia deviates considerably from its relatives not only in its coloration, but also in its wing shape . Even the good butterfly connoisseur Bates almost classified the species incorrectly when sorting his collection. Because many Dismorphia species outwardly resemble different Ithomiini species much more than their own relatives. The Ithomiini, however, belong to a completely different family , namely the noble butterflies (Nymphalidae).
Neither kinship nor a similar way of life could be considered as the reason for the great correspondence between Dismorphia and the Ithomiini. Bates looked for another explanation. The basic problem was why the butterflies resembled the noble butterflies of the Ithomiini tribe. He had observed that the Ithomiini species were very common, brightly colored, and flew so slowly that they were easy to catch. This puzzled the scholar .
Bates never saw the Ithomiini species captured by birds being actually eaten by them. From this he concluded that these butterflies must be inedible: the taste of disgust, toxicity, ... birds would quickly notice this, memorize the appearance of the inedible butterflies and avoid them in the future.
If there were a much rarer butterfly in the same area, which - although in principle edible - imitated the Ithomiini species in appearance and behavior, it would deceive the birds and likewise not be eaten. Such rarer butterflies were dismorphia .
European example of Batesian mimicry
In Europe, wasps , bees and bumblebees widespread. All of them, at least the spiked females, are "imitated" by some other, apparently completely defenseless insects . Poisonous and inedible species often have a conspicuous coloring, a so-called warning look . If this is imitated, one also speaks of false warning appearance.
Among the flies we know the hoverfly family , many species of which seem to specialize in “signal forgery” . Here you can find numerous species that look very similar to the defensive wasps and honeybees. The hover flies of the genus Eristalis imitate the European honey bee more or less well and are therefore also referred to as " dung bees "; their “rat tail larvae” usually develop in the manure from dung heaps. The similarity of numerous hover flies to wasps is even more striking. They have the bright yellow-black “warning signal” on the abdomen of their defensive role models and so often unsettle people who cannot distinguish between hoverflies and wasps.
However, if you take a closer look at hoverflies, they are relatively easy to identify as perfectly normal, harmless flies, because they lack some characteristic features of the wasps that belong to the order of hymenoptera , while hoverflies belong to the order of the two-winged flies . Wasps always have four wings and longer, kneeling antennae, while flies have only two main wings and stubby antennae. In addition, hoverflies can “float”, that is, remain in the same place in the air, similar to a helicopter.
Other insect species also use the wasps' “warning signal”. Among the beetles , for example, the billy wasp and some other longhorn beetles can be mistaken for wasps at first glance.
The imitation of the large hornets and wasps by the hornet glass-winged butterfly, a harmless butterfly, is so perfect that it almost resembles the dreaded hornet in size, color and wing position. Bumblebees are also imitated by a butterfly : by the bumblebee hawk .
The imitation of well-defended role models should not be limited to physical characteristics. Further similarities in behavior, living space and rhythm of life contribute to the fact that the role model and the imitator are confused with one another.
Inexperienced robbers eat the defenseless imitators, e.g. B. wasp-like hover flies, even very happy. But if toads and birds first hunted some of the defensive wasps, they then reject similar hoverflies for a long time. However, many birds and other predators can recognize colors and patterns very well and differentiate them precisely. Copycats are faced with the problem that they have to resemble their role models as much as possible.
Since the existence of non-poisonous imitators reduces the learning success or the avoidance behavior of predators, it is important that the numerical ratio is unbalanced, so that there are not too many harmless imitators.
Examples in plants
- Imitated eggs on the leaves of passion flower species as a defense against egg-laying butterflies of the genus Heliconius
Müllerian mimicry
The German biologist Johann Friedrich Theodor Müller (1821–1897) discovered in his observations of butterflies that animals that look the same do not always have to belong to the same species. In the course of the tribal history , inedible butterflies had acquired a common warning clothing so that the predators could no longer tell them apart. Therefore, the predator only had to have the bad experience with one animal and in future avoided all animals that looked the same. Both types benefit from this.
According to Lunau, there is no mimicry in the actual sense, but signal normalization, because here different species from different genera adapt to one another, which share their advantages.
Examples in the animal kingdom
- the poisonous butterflies of the Danainae subfamily found in America and East Asia .
- Ant spiders like the ant jumping spider
Examples in plants
Here it mainly affects flowers that look very similar and all z. B. Offer nectar.
- many species of Ranunculus ,
- in the alpine area: Dryas octopetala and Ranunculus campestris ,
- red bird flowers, e.g. B. Mimulus cardinalis , Penstemon campanulatus : Development from blue bumblebee flowers to avoid nectar competition
Mertens' mimicry
If a dangerous or harmless species adapts to a moderately dangerous species, one speaks of Mertensian mimicry. This name was established by the German zoologist Robert Mertens (1894–1975).
An example of this type of mimicry are the coral snakes of the genus Micrurus and Micruroides .
There are around 75 exceptionally colorful coral snake species on the American continent . Its bright colors, yellow and red, dominate alongside black. They can therefore easily be confused. These snakes are not closely related and belong to 18 different genera .
There is a differentiation of the danger of coral snakes according to three different groups:
- the highly poisonous coral otters ( Micrurus ) and Arizona coral otters ( Micruroides ),
- the only moderately poisonous species of the genus Erythrolamprus ,
- the completely harmless king snake ( Lampropeltis ) such as the triangular snake ( Lampropeltis triangulum ).
The real coral snakes have a very effective venom apparatus , and the venom is a deadly neurotoxin . But they are so small and their jaws are so weak that their bite, while very painful to humans, is not very dangerous.
The only moderately poisonous coral snakes are among the false snakes . In contrast to the venomous snakes, only the rear teeth are formed as venomous teeth. They have a relatively weak poison that is not fatal to humans. The coral snakes, like the completely harmless milk snake, are non-toxic snakes .
According to some researchers, in this case the highly poisonous (and non-poisonous) snakes have adapted in appearance to the moderately venomous. The highly poisonous snakes can (due to their poisonousness, but lower strength) defend themselves against smaller enemies with not too thick skin. But since these, if they are bitten, have a high probability of dying from the poison and therefore cannot learn from their behavior, the highly poisonous coral snakes benefit from being similar to the less poisonous species. A potential attacker might well have survived an encounter with specimens of the latter genus, but because of this unpleasant experience avoid snakes of this appearance. The non-poisonous coral snakes also enjoy protection due to their resemblance to the moderately poisonous species.
Peckham's mimicry
In contrast to the above-mentioned forms of mimicry, Peckham's mimicry (after George Peckham and Elizabeth Peckham , 1889), also known as aggressive mimicry , does not mean that attackers are averted; on the contrary, it has the effect of attracting other species.
One example is the monkfish Lophius spec. , a species of marine fish . It has a skin appendage on the isolated foremost ray of its dorsal fin, which it can move like a worm , with the result that other fish are attracted and thus become easy prey.
Another example are orchids of the genus Ophrys . With their petals they not only imitate the look and feel of female solitary bees and thus attract males who are ready to mate, but they also secrete even more effective sexual attractants ( insect pheromones ) than the real females. The males pollinate the flowers during the " mating act " (called pseudocopulation ). The petals of the flowers of the South African daisy family Gorteria diffusa also imitate female insects, which particularly attract males from the group of woolly flies (bombyliid flies).
The deceived individuals of a species (“signal receivers”) suffer, statistically speaking, a reproductive disadvantage. More of those individuals who were not fooled are procreating. The successful deceiver (“signal forger”) also enjoys higher chances of reproduction. This leads to an evolutionary race (galloping coevolution ), in which the quality of deception of the signal counterfeiters and the ability to differentiate between the signal receivers can reach a high level. Plants of the Rafflesia genus, for example, simulate a carcass with their flowers using color, size, smell and surface structure . Many flies that pass this bloom do not fall for the trick despite the combination of deceptive stimuli. To make recognition more difficult, the variation in the deceptive stimuli within a species ( intraspecific ) is often very high (no two Ophrys petals are the same).
Mimicry - not just aggressive - doesn't have to relate to looks either. Females of the firefly genus Photuris imitate the characteristic flare signals of females of other firefly species of the genus Photinus , attract their males and consume them. The males, for their part, often land in the immediate vicinity in order to get an idea of the female. Spider-eaters tug at the webs of other spiders with their legs, imitating prey caught in the web and eating the rushing web owner.
Chemical mimicry
The phenomenon of mimicry was described in the 19th century using conspicuous visual features that were mostly easily accessible to the observer and his scientific analysis. The deception of signal receivers with the help of other, non-visual signals, however, went unnoticed for a long time, although it was known that numerous animal species, for example, have a pronounced, sensitive olfactory perception . Only recently have studies been published on mimicry by exploiting “fake” chemical signals.
The orchid species Dendrobium sinense , which only occurs on the southern Chinese island of Hainan, attracts its pollinators , hornets of the Vespa bicolor species , by producing the chemical compound (Z) -11-eicosen-1-ol, among other things. This substance was first detected in a plant in 2009. However, it has long been known for being part of the "alarm pheromone" of honey bees, which hornets often hunt as prey. Behavioral experiments have shown that hornets are attracted to the scent of this compound. Further observations showed that hornets do not land on the flowers, but only briefly and violently hit the head against the red center of a flower, as if they were accessing prey and thereby contributing to the pollination of the flower.
The short-winged Trichopsenius frosti lives as a “subtenant” in the termite mounds of the termite species Reticulitermes flavipes . The hydrocarbon profile of his cuticula , which he himself synthesized , was described as being qualitatively equivalent to that of his "hosts".
The Germerblättrige Stendelwurz ( Epipactis veratrifolia ) attracts hoverflies by pheromone mimicry (Eng. Pheromone mimicry ) as pollinators. The plant produces the substances α- and β- pinene , β- myrcene and β- phellandrene , which are also the chemical alarm substances of aphids. Perception of these substances triggers the laying of eggs next to the supposed aphids in hoverflies, since hatching hoverfly larvae use the lice as food.
Molecular mimicry
Molecular mimicry refers to the fact that molecules on the surface of pathogens resemble or are identical to the body's own molecules. For the pathogen, this camouflages immunocompetent cells, which makes it difficult to recognize the germs as foreign structures. If these molecules are nevertheless recognized as antigen by the immune system , the subsequent immune reaction can be directed not only against the pathogen, but also against the body's own tissue. This process is also called cross-reaction and is considered to be a possible cause for the development of autoimmune diseases .
Molecular mimicry is discussed as a cause of diseases such as multiple sclerosis , rheumatoid arthritis and the gastric ulcer .
See also
literature
- Klaus Lunau : Warning, camouflaging, deceiving. Mimicry and other survival strategies in nature. Scientific Book Society, Darmstadt 2002, ISBN 3-534-14633-6 .
- Georges Pasteur: A classificatory review of mimicry systems. In: Annual Review of Ecology and Systematics. Volume 13, 1982, pp. 169-199, doi: 10.1146 / annurev.es.13.110182.001125 .
- Graeme D. Ruxton, Thomas N. Sherratt, Michael P. Speed: Avoiding Attack. The Evolutionary Ecology of Crypsis, Warning Signals and Mimicry. Oxford University Press, Oxford 2004, ISBN 0-19-852859-0 .
- Richard Irwin Vane-Wright: A unified classification of mimetic resemblances. In: Biological Journal of the Linnean Society. Volume 8, No. 1, 1976, pp. 25-56, doi: 10.1111 / j.1095-8312.1976.tb00240.x .
- Wolfgang Wickler : Mimicry. Imitation and deception in nature. Kindler, Munich 1971, ISBN 3-463-00469-0 (with a foreword by Konrad Lorenz ).
- Delbert Wiens: Mimicry in Plants. Chapter 6 in: Max K. Hecht, William C. Steere and Bruce Wallace (Eds.): Evolutionary Biology. Volume 11. Springer Science + Business Media, New York 1978, pp. 365-403, ISBN 978-1-4615-6958-9 .
- Helge Zabka: Camouflage and deception in plants and animals. Urania, Leipzig 1989, ISBN 3-332-00274-0 .
Web links
Individual evidence
- ↑ This definition follows Klaus Lunau, Warnen, Tarnen, Täuschen, p. 7.
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↑ FP Schiestl et al .: Sex pheromone mimicry in the early spider orchid (Ophrys sphegodes): patterns of hydrocarbons as the key mechanism for pollination by sexual deception. In: Journal of Comparative Physiology A. Volume 186, No. 6, 2000, pp. 567-574, doi: 10.1007 / s003590000112 .
Deceptive beauties. Max Planck Institute for Chemical Ecology, Research Report 2010, at: mpg.de - ^ HW Bates: Contributions to an insect fauna of the Amazon Valley. Lepidoptera: Heliconidae . In: Transactions of the Linnean Society (London) , Volume 23, No. 3, 1862, pp. 495 ff.
- ↑ Wolfgang Wickler: Mimicry. Imitation and deception in nature, Kindler, Munich 1971, ISBN 3-463-00469-0 , p. 243.
- ↑ http://www.stephenjaygould.org/library/vestiges/
- ↑ This can even lead to the separation of neighboring species, see: Philipp M. Schlüter u. a .: Stearoyl-acyl carrier protein desaturases are associated with floral isolation in sexually deceptive orchids. In: PNAS . Volume 108, No. 14, 2011, pp. 5696-5701, doi : 10.1073 / pnas.1013313108 .
- ↑ Allan G. Ellis, Steven D. Johnson: Floral Mimicry Enhances Pollen Export: The Evolution of Pollination by Sexual Deceit Outside of the Orchidaceae. In: The American Naturalist. Volume 176, 2010, pp. E143-E151, doi : 10.1086 / 656487 .
- ^ Konrad Dettner and Caroline Liepert: Chemical Mimicry and Camouflage. In: Annual Review of Entomology. Volume 39, 1994, pp. 129-154, doi: 10.1146 / annurev.en.39.010194.001021 .
- ↑ Jennifer Brodmann et al. a .: Orchid Mimics Honey Bee Alarm Pheromones in Order to Attract Hornets for Pollination. In: Current Biology. 19, No. 16, 2009, pp. 1368-1372, doi: 10.1016 / j.cub.2009.06.067 .
- ↑ Ralph W. Howard, CA McDaniel and Gary J. Blomquist: Chemical Mimicry as an Integrating Mechanism: Cuticular Hydrocarbons of a Termitophile and Its Host. In: Science. Volume 210, No. 4468, 1980, pp. 431-433, doi: 10.1126 / science.210.4468.431 .
- ↑ Ralph W. Howard, CA McDaniel and Gary J. Blomquist: Chemical Mimicry as an Integrating Mechanism for Three Termitophiles Associated With Reticulitermes Virginicus (Banks). In: Psyche. Vol. 89, No. 1-2, 1982, pp. 157-167, doi: 10.1155 / 1982/91358
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↑ Orchids trick hoverflies: Germer-leaved stendelwort chemically disguises itself as an aphid and thus attracts pollinators. On: mpg.de from October 14, 2010.
Johannes Stökl u. a .: Smells like aphids: orchid flowers mimic aphid alarm pheromones to attract hoverflies for pollination. In: Proceedings of the Royal Society B. Volume 278, No. 1709, 2010, pp. 1216-1222, doi: 10.1098 / rspb.2010.1770 . - ↑ JL Olson et al. a .: A virus-induced molecular mimicry model of multiple sclerosis. In: Current Topics in Microbiology and Immunology. 296, 2005, pp. 39-53, PMID 16323419 .