Batesian Mimicry
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Batesian mimicry is a form of
mimicry In evolutionary biology, mimicry is an evolved resemblance between an organism and another object, often an organism of another species. Mimicry may evolve between different species, or between individuals of the same species. Often, mimicry f ...
where a harmless species has evolved to imitate the warning signals of a harmful species directed at a
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 ...
of them both. It is named after the English naturalist
Henry Walter Bates Henry Walter Bates (8 February 1825, in Leicester – 16 February 1892, in London) was an English naturalist and explorer who gave the first scientific account of mimicry in animals. He was most famous for his expedition to the rainforests of ...
, after his work on
butterflies Butterflies are insects in the macrolepidopteran clade Rhopalocera from the Order (biology), order Lepidoptera, which also includes moths. Adult butterflies have large, often brightly coloured wings, and conspicuous, fluttering flight. The ...
in the
rainforest Rainforests are characterized by a closed and continuous tree canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforest can be classified as tropical rainforest or temperate rainfores ...
s of Brazil. Batesian mimicry is the most commonly known and widely studied of mimicry complexes, such that the word mimicry is often treated as synonymous with Batesian mimicry. There are many other forms however, some very similar in principle, others far separated. It is often contrasted with
Müllerian mimicry Müllerian mimicry is a natural phenomenon in which two or more well-defended species, often foul-tasting and sharing common predators, have come to mimic each other's honest warning signals, to their mutual benefit. The benefit to Müllerian ...
, a form of mutually beneficial convergence between two or more harmful species. However, because the mimic may have a degree of protection itself, the distinction is not absolute. It can also be contrasted with functionally different forms of mimicry. Perhaps the sharpest contrast here is with
aggressive mimicry Aggressive mimicry is a form of mimicry in which predators, parasites, or parasitoids share similar signals, using a harmless model, allowing them to avoid being correctly identified by their prey or host. Zoologists have repeatedly compare ...
where a predator or parasite mimics a harmless species, avoiding detection and improving its
foraging Foraging is searching for wild food resources. It affects an animal's Fitness (biology), fitness because it plays an important role in an animal's ability to survive and reproduce. Optimal foraging theory, Foraging theory is a branch of behaviora ...
success. The imitating species is called the ''mimic'', while the imitated species (protected by its toxicity, foul taste or other defenses) is known as the ''model''. The predatory species mediating indirect interactions between the mimic and the model is variously known as the '' ignalreceiver'', ''dupe'' or ''operator''. By parasitizing the honest warning signal of the model, the Batesian mimic gains an advantage, without having to go to the expense of arming itself. The model, on the other hand, is disadvantaged, along with the dupe. If impostors appear in high numbers, positive experiences with the mimic may result in the model being treated as harmless. At higher frequency there is also a stronger selective advantage for the predator to distinguish mimic from model. For this reason, mimics are usually less numerous than models, an instance of
frequency dependent selection Frequency-dependent selection is an evolutionary process by which the fitness of a phenotype or genotype depends on the phenotype or genotype composition of a given population. * In positive frequency-dependent selection, the fitness of a phenotyp ...
. Some mimetic populations have evolved multiple forms ( polymorphism), enabling them to mimic several different models and thereby to gain greater protection. Batesian mimicry is not always perfect. A variety of explanations have been proposed for this, including limitations in predators' cognition. While visual signals have attracted most study, Batesian mimicry can employ deception of any of the
sense A sense is a biological system used by an organism for sensation, the process of gathering information about the world through the detection of Stimulus (physiology), stimuli. (For example, in the human body, the brain which is part of the cen ...
s; some moths mimic the
ultrasound Ultrasound is sound waves with frequency, frequencies higher than the upper audible limit of human hearing range, hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hea ...
warning signals sent by unpalatable moths to
bat Bats are mammals of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most ...
predators, constituting auditory Batesian mimicry, while some weakly electric fish appear to mimic the
electrolocation Electroreception and electrogenesis are the closely-related biological abilities to perceive electrical stimuli and to generate electric fields. Both are used to locate prey; stronger electric discharges are used in a few groups of fishes to stu ...
signals of strongly electric fish, probably constituting electrical mimicry.


Historical background

Henry Walter Bates Henry Walter Bates (8 February 1825, in Leicester – 16 February 1892, in London) was an English naturalist and explorer who gave the first scientific account of mimicry in animals. He was most famous for his expedition to the rainforests of ...
(1825–1892) was an English
explorer Exploration refers to the historical practice of discovering remote lands. It is studied by geographers and historians. Two major eras of exploration occurred in human history: one of convergence, and one of divergence. The first, covering most ...
- naturalist who surveyed the
Amazon rainforest The Amazon rainforest, Amazon jungle or ; es, Selva amazónica, , or usually ; french: Forêt amazonienne; nl, Amazoneregenwoud. In English, the names are sometimes capitalized further, as Amazon Rainforest, Amazon Forest, or Amazon Jungle. ...
with Alfred Russel Wallace in 1848. While Wallace returned in 1852, Bates remained for over a decade. His field research included collecting almost a hundred species of
butterflies Butterflies are insects in the macrolepidopteran clade Rhopalocera from the Order (biology), order Lepidoptera, which also includes moths. Adult butterflies have large, often brightly coloured wings, and conspicuous, fluttering flight. The ...
from the families
Ithomiinae Ithomiini is a butterfly tribe in the nymphalid subfamily Danainae. It is sometimes referred to as the tribe of clearwing butterflies or glasswing butterflies. Some authors consider the group to be a subfamily (Ithomiinae). These butterflies are ...
and
Heliconiinae The Heliconiinae, commonly called heliconians or longwings, are a subfamily of the brush-footed butterflies (family Nymphalidae). They can be divided into 45–50 genera and were sometimes treated as a separate family Heliconiidae within the P ...
, as well as thousands of other insects specimens. In sorting these butterflies into similar groups based on appearance, inconsistencies began to arise. Some appeared superficially similar to others, even so much so that Bates could not tell some species apart based only on wing appearance. However, closer examination of less obvious morphological characters seemed to show that they were not even closely related. Shortly after his return to England he read a paper on his theory of mimicry at a meeting of the
Linnean Society of London The Linnean Society of London is a learned society dedicated to the study and dissemination of information concerning natural history, evolution, and taxonomy. It possesses several important biological specimen, manuscript and literature colle ...
on 21 November 1861, which was then published in 1862 as 'Contributions to an Insect Fauna of the Amazon Valley' in the society's '' Transactions''.; Reprint: He elaborated on his experiences further in ''
The Naturalist on the River Amazons ''The Naturalist on the River Amazons'', subtitle (titling), subtitled ''A Record of the Adventures, Habits of Animals, Sketches of Brazilian and Indian Life, and Aspects of Nature under the Equator, during Eleven Years of Travel'', is an 1863 ...
''. Bates put forward the hypothesis that the close resemblance between unrelated species was an
antipredator adaptation Anti-predator adaptations are mechanisms developed through evolution that assist prey organisms in their constant struggle against predators. Throughout the animal kingdom, adaptations have evolved for every stage of this struggle, namely by avo ...
. He noted that some species showed very striking coloration, and flew in a leisurely manner, almost as if taunting predators to eat them. He reasoned that these butterflies were unpalatable to birds and other
insectivore A robber fly eating a hoverfly An insectivore is a carnivorous animal or plant that eats insects. An alternative term is entomophage, which can also refer to the human practice of eating insects. The first vertebrate insectivores wer ...
s, and were thus avoided by them. He extended this logic to forms that closely resembled such protected species, mimicking their warning coloration but not their toxicity. This naturalistic explanation fitted well with the recent account of
evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
by Wallace and
Charles Darwin Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended fr ...
, as outlined in his famous 1859 book ''
The Origin of Species ''On the Origin of Species'' (or, more completely, ''On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life''),The book's full original title was ''On the Origin of Species by Me ...
''. Because this
Darwinian Darwinism is a theory of biological evolution developed by the English naturalist Charles Darwin (1809–1882) and others, stating that all species of organisms arise and develop through the natural selection of small, inherited variations that ...
explanation required no supernatural forces, it met with considerable criticism from anti-evolutionists, both in academic circles and in the broader social realm.


Aposematism

Most living things have predators and therefore are in a constant
evolutionary arms race In evolutionary biology, an evolutionary arms race is an ongoing struggle between competing sets of co-evolving genes, phenotypic and behavioral traits that develop escalating adaptations and counter-adaptations against each other, resembling an ...
to develop
antipredator adaptation Anti-predator adaptations are mechanisms developed through evolution that assist prey organisms in their constant struggle against predators. Throughout the animal kingdom, adaptations have evolved for every stage of this struggle, namely by avo ...
s, while the predator adapts to become more efficient at defeating the prey's adaptations. Some organisms have evolved to make
detection {{Unreferenced, date=March 2018 In general, detection is the action of accessing information without specific cooperation from with the sender. In the history of radio communications, the term " detector" was first used for a device that detected ...
less likely, for example by
nocturnality Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sens ...
and
camouflage Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the ...
. Others have developed chemical defences such as the deadly
toxin A toxin is a naturally occurring organic poison produced by metabolic activities of living cells or organisms. Toxins occur especially as a protein or conjugated protein. The term toxin was first used by organic chemist Ludwig Brieger (1849– ...
s of certain snakes and wasps, or the noxious scent of the
skunk Skunks are mammals in the family Mephitidae. They are known for their ability to spray a liquid with a strong, unpleasant scent from their anal glands. Different species of skunk vary in appearance from black-and-white to brown, cream or ginge ...
. Such prey often send clear and honest warning signals to their attackers with conspicuous
aposematic Aposematism is the advertising by an animal to potential predators that it is not worth attacking or eating. This unprofitability may consist of any defences which make the prey difficult to kill and eat, such as toxicity, venom, foul taste o ...
(warning) patterns. The brightness of such warning signs is correlated with the level of toxicity of the organism. In Batesian mimicry, the mimic effectively copies the coloration of an aposematic animal, known as the model, to deceive predators into behaving as if it were distasteful. The success of this dishonest display depends on the level of toxicity of the model and the abundance of the model in the geographical area. The more toxic the model is, the more likely it is that the predator will avoid the mimic. The abundance of the model species is also important for the success of the mimic because of
frequency dependent selection Frequency-dependent selection is an evolutionary process by which the fitness of a phenotype or genotype depends on the phenotype or genotype composition of a given population. * In positive frequency-dependent selection, the fitness of a phenotyp ...
. When the model is abundant, mimics with imperfect model patterns or slightly different coloration from the model are still avoided by predators. This is because the predator has a strong incentive to avoid potentially lethal organisms, given the likelihood of encountering one. However, in areas where the model is scarce or locally extinct, mimics are driven to accurate aposematic coloration. This is because predators attack imperfect mimics more readily where there is little chance that they are the model species. Frequency dependent selection may also have driven Batesian mimics to become polymorphic in rare cases where a single genetic switch controls appearance, as in the swallowtail butterflies (the
Papilionidae Swallowtail butterflies are large, colorful butterflies in the family Papilionidae, and include over 550 species. Though the majority are tropical, members of the family inhabit every continent except Antarctica. The family includes the larg ...
) such as the
pipevine swallowtail ''Battus philenor'', the pipevine swallowtail or blue swallowtail, Retrieved April 19, 2018. is a swallowtail butterfly found in North America and Central America. This butterfly is black with iridescent-blue hindwings. They are found in many di ...
.


Classification and comparisons

Batesian mimicry is a case of protective or defensive mimicry, where the mimic does best by avoiding confrontations with the signal receiver. It is a ''disjunct'' system, which means that all three parties are from different species. An example would be the
robber fly The Asilidae are the robber fly family, also called assassin flies. They are powerfully built, bristly flies with a short, stout proboscis enclosing the sharp, sucking hypopharynx. The name "robber flies" reflects their notoriously aggressive pre ...
'' Mallophora bomboides'', which is a Batesian mimic of its
bumblebee A bumblebee (or bumble bee, bumble-bee, or humble-bee) is any of over 250 species in the genus ''Bombus'', part of Apidae, one of the bee families. This genus is the only extant group in the tribe Bombini, though a few extinct related gener ...
model and prey, ''B. americanorum'' (now more commonly known as ''
Bombus pensylvanicus ''Bombus pensylvanicus'', the American bumblebee, is a threatened species of bumblebee native to North America. It occurs in eastern Canada, throughout much of the Eastern United States, and much of Mexico.Hatfield, R., et al. 2015''Bombus pensyl ...
''), which is noxious to predators due to its sting. Batesian mimicry stands in contrast to other forms such as
aggressive mimicry Aggressive mimicry is a form of mimicry in which predators, parasites, or parasitoids share similar signals, using a harmless model, allowing them to avoid being correctly identified by their prey or host. Zoologists have repeatedly compare ...
, where the mimic profits from interactions with the signal receiver. One such case of this is in
fireflies The Lampyridae are a family of elateroid beetles with more than 2,000 described species, many of which are light-emitting. They are soft-bodied beetles commonly called fireflies, lightning bugs, or glowworms for their conspicuous production ...
, where females of one species mimic the mating signals of another species, deceiving males to come close enough for them to eat. Mimicry sometimes does not involve a predator at all though. Such is the case in ''dispersal mimicry'', where the mimic once again benefits from the encounter. For instance, some fungi have their spores dispersed by insects by smelling like carrion. In protective mimicry, the meeting between mimic and dupe is not such a fortuitous occasion for the mimic, and the signals it mimics tend to lower the probability of such an encounter. A case somewhat similar to Batesian mimicry is that of mimetic weeds, which imitate agricultural crops. In weed or
Vavilovian mimicry In plant biology, Vavilovian mimicry (also crop mimicry or weed mimicry) is a form of mimicry in plants where a weed evolves to share one or more characteristics with a domesticated plant through generations of artificial selection. It is name ...
, the weed survives by having seeds which
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 ...
machinery identifies as belonging to the crop. Vavilovian mimicry is not Batesian, because man and crop are not enemies. By contrast, a leaf-mimicking plant, the chameleon vine, employs Batesian mimicry by adapting its leaf shape and colour to match that of its host to deter herbivores from eating its edible leaves. Another analogous case within a single species has been termed ''Browerian mimicry'' (after Lincoln P. Brower and Jane Van Zandt BrowerBrower, L. P. (1970) Plant poisons in a terrestrial food chain and implications for mimicry theory. In K. L. Chambers (ed) ''Biochemical Coevolution'' Corvallis, OR: Oregon State Univ. pp. 69-82.). This is a case of
automimicry In zoology, automimicry, Browerian mimicry, or intraspecific mimicry, is a form of mimicry in which the same species of animal is imitated. There are two different forms. In one form, first described by Lincoln Brower in 1967, weakly-defended m ...
; the model is the same species as its mimic. Equivalent to Batesian mimicry within a single species, it occurs when there is a ''palatability spectrum'' within a population of harmful prey. For example,
monarch A monarch is a head of stateWebster's II New College DictionarMonarch Houghton Mifflin. Boston. 2001. p. 707. Life tenure, for life or until abdication, and therefore the head of state of a monarchy. A monarch may exercise the highest authority ...
(''Danaus plexippus'') caterpillars feed on
milkweed ''Asclepias'' is a genus of herbaceous, perennial, flowering plants known as milkweeds, named for their latex, a milky substance containing cardiac glycosides termed cardenolides, exuded where cells are damaged. Most species are toxic to humans ...
species of varying toxicity. Some feed on more toxic plants and store these toxins within themselves. The more palatable caterpillars thus profit from the more toxic members of the same species. Another important form of protective mimicry is
Müllerian mimicry Müllerian mimicry is a natural phenomenon in which two or more well-defended species, often foul-tasting and sharing common predators, have come to mimic each other's honest warning signals, to their mutual benefit. The benefit to Müllerian ...
, discovered by and named after the naturalist
Fritz Müller Johann Friedrich Theodor Müller (31 March 1822 – 21 May 1897), better known as Fritz Müller, and also as Müller-Desterro, was a German biologist who emigrated to southern Brazil, where he lived in and near the German community of Blumenau, ...
. In Müllerian mimicry both model and mimic are aposematic, so mimicry may be mutual, does not necessarily constitute a bluff or deception and as in the wasps and bees may involve many species in a mimicry ring.


Imperfect Batesian mimicry

In imperfect Batesian mimicry, the mimics do not exactly resemble their models. An example of this is the fly '' Spilomyia longicornis'', which mimics
vespid The Vespidae are a large (nearly 5000 species), diverse, cosmopolitan family of wasps, including nearly all the known eusocial wasps (such as ''Polistes fuscatus'', ''Vespa orientalis'', and ''Vespula germanica'') and many solitary wasps. Each ...
wasps. However, it is not a perfect mimic. Wasps have long black antennae and this fly does not. Instead, they wave their front legs above their heads to look like the antennae on the wasps. Many reasons have been suggested for imperfect mimicry. Imperfect mimics may simply be evolving towards perfection. They may gain advantage from resembling multiple models at once. Humans may evaluate mimics differently from actual predators. Mimics may confuse predators by resembling both model and nonmimic at the same time (satiric mimicry). Kin selection may enforce poor mimicry. The selective advantage of better mimicry may not outweigh the advantages of other strategies like thermoregulation or camouflage. Only certain traits may be required to deceive predators; for example, tests on the sympatry/
allopatry Allopatric speciation () – also referred to as geographic speciation, vicariant speciation, or its earlier name the dumbbell model – is a mode of speciation that occurs when biological populations become geographically isolated from ...
border (where the two are in the same area, and where they are not) of the mimic ''
Lampropeltis elapsoides The scarlet kingsnake or scarlet milk snake (''Lampropeltis elapsoides'') is a species of kingsnake found in the southeastern and eastern portions of the United States. Like all kingsnakes, they are nonvenomous. They are found in pine flatwoods, ...
'' and the model ''
Micrurus fulvius ''Micrurus fulvius'', commonly known as the eastern coral snake, Behler John L.; King, F. Wayne (1979). ''The Audubon Society Field Guide to North American Reptiles and Amphibians''. New York: Alfred A. Knopf. 743 pp., 657 color plates. LCCCN 7 ...
'' showed that color proportions in these snakes were important in deceiving predators but that the order of the colored rings was not.


Acoustic mimicry

Predators may identify their prey by sound as well as sight; mimics have accordingly evolved to deceive the
hearing Hearing, or auditory perception, is the ability to perceive sounds through an organ, such as an ear, by detecting vibrations as periodic changes in the pressure of a surrounding medium. The academic field concerned with hearing is audit ...
of their predators.
Bat Bats are mammals of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most ...
s are nocturnal predators that rely on echolocation to detect their prey. Some potential prey are unpalatable to bats, and produce an ultrasonic aposematic signal, the auditory equivalent of warning coloration. In response to echolocating red bats and big brown bats,
tiger moth The de Havilland DH.82 Tiger Moth is a 1930s British biplane designed by Geoffrey de Havilland and built by the de Havilland Aircraft Company. It was operated by the Royal Air Force (RAF) and other operators as a primary trainer aircraft. ...
s such as '' Cycnia tenera'' produce warning sounds. Bats learn to avoid the harmful moths, but similarly avoid other species such as some pyralid moths that produce such warning sounds as well. Acoustic mimicry complexes, both Batesian and Müllerian, may be widespread in the auditory world.


Electrical mimicry

The
electric eel The electric eels are a genus, ''Electrophorus'', of neotropical freshwater fish from South America in the family Gymnotidae. They are known for their ability to stun their prey by generating electricity, delivering shocks at up to 860 volt ...
, ''Electrophorus'', is capable of delivering a powerful electric shock that can stun or kill its prey. Bluntnose knifefishes, ''
Brachyhypopomus ''Brachyhypopomus'' is a genus of fish in the family Hypopomidae (bluntnose knifefish) native primarily to tropical and subtropical South America (south to the Río de la Plata Basin), although a single species, ''B. occidentalis'', also occurs ...
'', create an electric discharge pattern similar to the low voltage
electrolocation Electroreception and electrogenesis are the closely-related biological abilities to perceive electrical stimuli and to generate electric fields. Both are used to locate prey; stronger electric discharges are used in a few groups of fishes to stu ...
discharge of the electric eel. This is thought to be Batesian mimicry of the powerfully-protected electric eel.


See also

* Phylogenetics of mimicry * ''
Papilio dardanus ''Papilio dardanus'', the African swallowtail, mocker swallowtail or flying handkerchief, is a species of butterfly in the family Papilionidae (the swallowtails). The species is broadly distributed throughout Sub-Saharan Africa. The British e ...
'' (females mimic multiple model species) * Locomotor mimicry


Notes


References


Further reading

* Cott, H.B. (1940) ''Adaptive Coloration in Animals''. Methuen and Co, Ltd., London Provides many examples of Batesian Mimicry * For a historical perspective. * Wickler, W. (1968) ''Mimicry in Plants and Animals'' (Translated from the German) McGraw-Hill, New York. Especially the first two chapters. * Edmunds, M. 1974. ''Defence in Animals: A Survey of Anti-Predator Defences''. Harlow, Essex & NY: Longman 357 p.  Chapter 4 discusses this phenomenon. * A detailed discussion of the different forms of mimicry. * Ruxton, G. D.; Speed, M. P.; Sherratt, T. N. (2004). ''Avoiding Attack. The Evolutionary Ecology of Crypsis, Warning Signals and Mimicry''. Oxford: Oxford University Press. Chapter 10 and 11 provide an up-to-date synopsis.


External links


Review of Contributions to an insect fauna of the Amazon valley by Charles Darwin
The Complete Works of Charles Darwin Online.
Biographical sketch of Bates, with picture
{{DEFAULTSORT:Batesian Mimicry Mimicry Antipredator adaptations Chemical ecology