Batesian Mimicry

In Batesian mimicry, for instance, a harmless prey species evolves a resemblance to a harmful species, as when a harmless king ophidian evolves the cherry-red, yellow, and blackness pattern of a venomous coral snake (Greene and McDiarmid, 1981).

From: Encyclopedia of Animal Beliefs (Second Edition) , 2019

Butterflies

Philip J. DeVries , in Encyclopedia of Biodiversity (Second Edition), 2001

Glossary

Aposematic

Describing an organism that is rendered less susceptible to predation by advertisement its obvious unpalatability.

Batesian mimicry

A form of mimicry in which the target organism is rendered less susceptible to predation by its resemblance in morphology or coloration to a different species that is unpalatable.

Cryptic

Describing an organism that is concealed or obscured by the similarity of its appearance to the surrounding environment.

Müllerian mimicry

A form of mimicry in which two or more unpalatable species resemble each other, with the outcome that predators are more than likely to avoid any species with this appearance.

Myrmecophily

Ability to class symbiotic associations with ants.

Vibratory papillae

Mobile, grooved, rod-like appendages arising from the distal edge of the first thoracic segment, used for communicating.

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Coevolution

Douglas J. Futuyma , André Levy , in Encyclopedia of Biodiversity, 2001

IV.B. Mimicry

Another form of coevolution among prey species subject to common predators is the coevolution of mimicry. 2 common forms of mimicry are typically distinguished. Batesian mimicry refers to the convergence of palatable mimic species on distasteful models. Predators learn to avoid certain prey shape and colour patterns they experienced every bit distasteful and mimics of such patterns can profit from this aversion. Monarch butterfly larvae, Danaus plexippus, feed almost exclusively on milkweed, from which they sequester cardiac glycosides. These toxic compounds are retained in the adult and vertebrate predators quickly learn to avert both monarch adults and the more palatable mimetic viceroy butterfly, Limenitis archippus. Cleaner fish provide a variation on Batesian mimicry. In coral reefs in the Pacific, many fish allow cleaner fish, such as the bounding main swallow (Labroides dimidiatus), to feed on parasites on their bodies and even in the interior of their mouths. The sabre-toothed blenny (Aspidontus taeniatus) mimics the white-and-black-striped coloration and swimming pattern of Labroides. By taking reward of the passive beliefs of fish toward the model, it is able to approach fish and bite off pieces of tissue. Labroides and Aspidontus evidence parallel variation in color patterns across different geographic areas, which strongly suggests that indeed the mimic is converging on the model. It is a matter of discussion, however, whether mimics will instill development in the model, which might be expected to evolve differences that lessen the resemblance.

Müllerian mimicry refers to the convergence toward a similar pattern among unpalatable species. Faced with several undesirable species that look akin, a predator must learn a lower number of patterns to avoid. Evolution in all casualty species leads toward a mutual pattern, and so warrants the designation of coevolution. One of the most striking cases of Müllerian mimicry, mentioned earlier, is the convergence betwixt the neotropical butterflies Heliconius erato and H. melpomene. Despite differences in life history, these species share a common fly color pattern that varies geographically in parallel. One of the species, H. erato, is commonly the most abundant where both species co-occur, raising the possibility that parallel evolution occurred by mere convergence of the rarer H. melpomene toward a mutual model. However, comparison between sympatric and allopatric populations of H. erato in Central American revealed that the width of the H. erato yellow hind-wing bar converges upon that of H. melpomene when in sympatry, suggesting that both species converge on each other.

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Decision-Making and Learning: The Peak Shift Behavioral Response

Due south.Thousand. Lynn , in Encyclopedia of Animate being Behavior, 2010

Evolution of mimicry and crypsis

Bumblebees (Bombus impatiens ) foraging for nectar exhibited acme shift when choosing the flowers to visit (and thus pollinate). In a laboratory written report implementing a Batesian mimicry organisation, bees were trained to forage on artificial flowers (colored paper disks) under different signal parameter sets. During training, positions of 36 S+ and Southward– flowers, present simultaneously, were randomized in a half dozen  ×   6 array on the floor of a flying cage. 'Baseline' bees received an arbitrary parameter prepare specifying the color and number of S+ and Due south− bloom types, and the sugar-water reward for visiting the two blossom types. Three groups of comparison bees each differed from baseline by manipulating one of the three signal parameters: increased variance of S– advent (three S– flower colors used, whereas baseline used i), decreased relative abundance of S+ (28% of stimuli were S+ flowers, whereas baseline had 50%), and decreased reward for correct detection of S+ (33% sucrose concentration, whereas baseline used 50%). When tested on a range of nine colors (iv exemplars each in random positions in the flight cage), the baseline bees exhibited peak shift relative to a command group that had received no S– training. Furthermore, every bit predicted by the signals arroyo, the comparison bees exhibited larger top shift and surface area shift over and above that exhibited past the baseline bees, in accord with the increased signal-borne risk of their training regimes. Simultaneous presentation of all exam stimuli was used as a manner to mitigate range effects. Too, range effects do not explain the greater shift produced by increased signal variance (which maintained the same adaptation level as the baseline status). The results betoken that in natural situations of mimicry (2 signals resembling one another) or crypsis (a betoken being difficult to distinguish from noise), peak shift tin influence the development of signaling traits.

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Book 3

S.One thousand. Lynn , in Encyclopedia of Beast Behavior (Second Edition), 2017

Evolution of Mimicry and Crypsis

Bumblebees (Bombus impatiens ) foraging for nectar exhibited peak shift when choosing the flowers to visit (and thus pollinate). In a laboratory report implementing a Batesian mimicry system, bees were trained to provender on artificial flowers (colored newspaper disks) under unlike signal parameter sets. During training, positions of 36 S+ and Due south− flowers, present simultaneously, were randomized in a vi×6 assortment on the floor of a flight cage. "Baseline" bees received an capricious parameter set specifying the color and number of S+ and S− blossom types, and the sugar-water reward for visiting the ii blossom types. Three groups of comparison bees each differed from baseline by manipulating one of the three betoken parameters: increased variance of Due south− appearance (three Southward− blossom colors used, whereas baseline used one), decreased relative abundance of S+ (28% of stimuli were Southward+ flowers, whereas baseline had l%), and decreased reward for correct detection of S+ (33% sucrose concentration, whereas baseline used l%). When tested on a range of nine colors (four exemplars each in random positions in the flight muzzle), the baseline bees exhibited tiptop shift relative to a control group that had received no Southward− preparation. Furthermore, as predicted past the signals approach, the comparison bees exhibited larger superlative shift and area shift over and above that exhibited by the baseline bees, in accordance with the increased signal-borne risk of their grooming regimes. Simultaneous presentation of all test stimuli was used as a way to mitigate range effects. Also, range effects do not explicate the greater shift produced by increased point variance (which maintained the same adaptation level equally the baseline status). The results indicate that in natural situations of mimicry (two signals resembling ane another) or crypsis (a signal being difficult to distinguish from noise), peak shift tin can influence the evolution of signaling traits.

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Moths

David 50. Wagner , in Encyclopedia of Biodiversity (Second Edition), 2013

Glossary

Aposematic

Warningly colored; boldly colored, usually involving reds, oranges, or yellows, as well as black and white; less commonly with only black and white blueprint elements.

Batesian mimicry

Evolutionary phenomenon whereby a palatable species comes to resemble a distasteful, toxic, or otherwise protected species and thereby gains some protection from predators.

Congener

A member of a shared genus.

Crochets

Hook-like structures at the ends of abdominal prolegs for engaging silk and other substrates.

Detritivore

An fauna (larva in this article) that feeds on expressionless organic droppings; although the term covers both constitute or animal matter, in moths the term is especially apt to utilize to leaf litter feeding.

Diapauses

Period of hormonally controlled inactivity generally associated with atmospheric condition atmospheric condition that are unfavorable to survival or reproduction. Oft induced by shortening 24-hour interval lengths in late summer and fall, and broken by warm temperatures in leap.

Hemolymph

Translucent yellow to green fluid that fills an insect'southward body, sharing functions of blood and lymphic systems, merely differing in that information technology does not transport oxygen in almost insects.

Hypermetamorphic

A life bike that includes two or more larval forms, with each often specialized for a different feeding function (and larval ecology).

Instar

A larval stage; the kickoff instar hatches from the egg and on molting enters the second instar. Well-nigh moths undergo v or six instars prior to pupation; every bit few as three and more than a dozen occur in diverse lineages.

Maxillae

The 2nd pair of mouthparts, located between the mandibles and the labium; the third pair of mouthparts.

Monophyletic

A group with a unmarried evolutionary origin that includes the mutual ancestor and all of that ancestor's descendants.

Mullerian mimicry

Evolutionary phenomenon whereby distasteful, toxic, or otherwise protected species come to resemble one another. In so doing the members of Mullerian mimicry complex gain past more efficiently educating local predators.

Natural group

Monophyletic; group with a common origin (i.east., having a shared common antecedent).

Oviposit

To lay an egg or ovum.

Parasitoid

Predator that lives internally or externally on its host. Parasitoids are parasite-like in that they are smaller than their hosts, feed from inside or on the host's torso, and often do so over a catamenia of weeks or months, but functionally they are predators because they about always kill their host (prey).

Pharate

A "cloaked" or hidden stage, for instance, the adult moth prior to its emergence from the pupa (which in some noctuid moths can be delayed by more than seven months).

Pheromone

A chemical released by one individual that elicits a response in a second individual of the same species.

Polyphagous

Eating plants from more than ii unrelated plant families.

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Butterflies

Philip J. DeVries , in Encyclopedia of Biodiversity, 2001

Six. Butterfly Variety and Habitat Destruction

Information technology is obvious that the evolution of butterfly diverseness is based on historical and gimmicky interactions with many species. These biological interactions include plant and/or insect hosts, co-mimics in Batesian and Müllerian mimicry complexes, predators, and parasites. Collywobbles take likewise evolved within and adapted to a great many biomes, habitats, and microhabitats, ranging from the multilevels inside lush tropical rain forests to starkly dry deserts and subarctic tundra.

Habitat destruction e'er has profound effects on the biological communities that inhabit them, and collywobbles are no exception. Like all organisms, butterflies live, evolve, and diversify within dynamic biological systems, and as such they cannot be studied as art objects or protected as inventoried stock. To date, collywobbles have served equally tools for understanding the diversification of life on Globe and the fundamental interactions among species. However, our future understanding of butterfly diversity will depend on a renewed interest in studying them in the natural world and valuing the habitats in which they occur.

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Volume 4

Graeme D. Ruxton , in Encyclopedia of Animal Behavior (2nd Edition), 2019

Batesian Mimicry

If the predator learns that a certain signal is associated with unattractive prey and thus avoids attacking individuals that carry that indicate, then an undefended species that also carried this same signal would gain protection from predators. This is the miracle of Batesian mimicry. In this example, there is asymmetry in the relationship between the two species with the aforementioned signal: the defended (or otherwise unattractive) 1 is called the model, and its signal is copied by another undefended species, the mimic. If, while the predator is learning nigh the bespeak involved, it finds a substantial proportion of the signal-begetting individuals to exist generally bonny as casualty (i.e., to be mimics), then the predator volition not larn to avert bearers of this indicate. Thus, we should look Batesian mimics to be at low population density compared to their models and perchance emerge later in a season, after the learned aversion by predators has been achieved. The more common the model is and the more than unpleasant it is for the predator to attack it, the more effective the learned aversion will be and the more readily a population of mimics can be supported. The model likely pays a price for this mimicry. Even if the predator does somewhen learn to avoid individuals bearing the bespeak, if during the learning period a small-scale number of sampled casualty individuals are actually palatable mimics, then the process of learning is likely to exist slowed, and this may mean that a larger number of models experience the cost of beingness attacked.

If the model is disadvantaged past mimicry, why does not the model evolve equally quickly away from the mimic as the mimic evolves toward information technology? One explanation is based on the relative success of rare mimic and rare model mutants. Whatever alter in the mimic phenotype toward the model might provide a selective advantage (because there is an increased chance of being mistakenly misclassified as a model). In contrast, major mutants of the model species abroad from the mimic will not spread as rapidly because they are rare and not recognized equally distasteful, and thus may face reduced fitness through higher predation adventure. Fifty-fifty if models could readily evolve away from mimics, it is unlikely that models could always 'shake off' mimicry completely since choice to avert mimicry depends on the presence of a high mimetic burden in the first identify. In essence, Batesian mimicry may exist a race that cannot be won by models unless they adopt forms than mimics cannot readily evolve toward.

The mimicry need non be a perfect replica of the model in club to gain protection; it may just accept to be like enough to put uncertainty in the predator'southward mind. This phenomenon of imperfect mimicry tin can clearly exist seen in hoverflies, which, although they have the distinctive colored stripe design of wasps, can frequently exist readily distinguished from wasps by humans on the footing of differences in trunk proportions. Such imperfect mimicry may be possible when the model is peculiarly unpleasant for predators, making the predators much less probable to experiment with something that just might be a model.

Several Batesian mimicking species are polymorphic, with different morphs in different geographical regions mimicking different local models. This polymorphism may help to keep the local density of mimics of a detail model low in comparison to the population density of their model. Sometimes, Batesian mimicry may be express to 1 sexual practice. This dimorphism may stem from differential exposure to predators betwixt the sexes and/or one sexual activity having a greater need for coloration for other purposes. For example, male butterflies of such a species may have their appearance constrained past the need to utilise coloration to attract mates, whereas the appearance of females may be less constrained and can be mimetic of another species.

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Self-Defense

Michael D. Brood , Janice Moore , in Beast Behavior (Second Edition), 2016

x.iv Mimicry and Diversion

Unpleasant experiences and even noxious tastes have given rise to one of the virtually fascinating areas of mimicry considering animals experience lower predation chance when they look like bad tasting, dangerous, or poisonous animals. This mimicry seems to work whether or not the mimic itself tastes bad. Henry Walter Bates, a contemporary of Darwin's, first described the mimicry that bears his proper name— Batesian mimicry . In this type of mimicry, a palatable casualty (the mimic) is favored past natural choice if it resembles an unpalatable species (the model); information technology will benefit if predators learn that an animate being that looks similar the model is not worth eating. For this to occur, the model needs to be relatively abundant. At the other extreme, Muellerian mimicry, named subsequently Fritz Mueller, occurs when two unpalatable species converge on an advent; both may do good by increasing the number of "teachers" that are informing predator-"students" about these bad-tasting prey. In sum, mimicry covers a broad range of evolutionary possibilities (Figure 10.eighteen). Batesian mimicry, in which a beneficial food particular looks like or behaves similar a distasteful or poisonous species, and Muellerian mimicry, in which noxious animals converge on the same advent or behavior, are important self-defenses; examples range throughout the fauna world. 1 hypothesis for the brightly colored but nontoxic rex snake is that it may mimic the highly poisonous coral serpent. Both have red, yellow, and blackness bands in differing arrangements: "Ruby-red and yellow, kill a fellow; carmine and blackness, venom lack." Many collywobbles are Batesian mimics of other butterflies, whereas yellow or orangish stripes on the abdomen denote Muellerian mimicry amid stinging insects.

Figure x.18. Stinging insects and their mimics. (A) This is a yellowjacket, a wasp with a very painful sting. (B) A honeybee. (C and D) Flies that mimic stinging insects.

 Photos: (A) Whitney Cranshaw, Colorado State University, Bugwood.org; (B) Deng Xiaobao; (C) Susan Ellis, Bugwood.org; (D) Johnny N. Dell, Bugwood.org.

Fundamental Term

Batesian mimicry is a beliefs in which a benign food item (casualty) looks like or behaves like a distasteful or poisonous species.

Cardinal Term

Muellerian mimicry is a behavior in which noxious animals converge on the same advent or behavior.

Probably every student has experienced a wasp or bee sting and learned, through that feel, to acquaintance xanthous/orange and black banding in a flying insect with pain. Birds and nonhuman mammals make the same association; this results in protection for stinging species with like appearances (Muellerian mimicry) and for nonstinging species that look like a bee or wasp (Batesian mimicry). Color and shape tell role of the story, but for a species to be a actually convincing mimic of a stinging insect, behavior comes into play. Flies that look like bees add to their deceptive story by beingness around flowers. Flies requite themselves away to knowledgeable humans (particularly entomologists) by having a dissimilar pitch to their buzz and a propensity to hover rather than to sprint when they wing. The extent to which a skilful morphological mimic is besides a good behavioral mimic often determines its success.

Give-and-take Point: Batesian or Muellerian Mimics?

Experimentally, it can be hard to find whether a mimic is Batesian or Muellerian. 41 For many years, scientists thought that Viceroy butterflies were Batesian mimics of Monarch butterflies (Figure 10.19). More recently, studies take shown that Viceroys tin can be quite unpalatable and that some populations of Monarchs tin be tasty to birds. In that location are really many instances all along this continuum between palatable/unpalatable and unpalatable/unpalatable pairings in which mimics may be unpalatable, simply not as unpalatable as models. In fact, palatability tin can vary even within a population, so the story in at least some cases is not as swell as that presented here. Yet, mimicry does happen, and in near cases, the thing that is mimicked is the model's aposematic advertisement of unpalatability. Practise your own literature search to explore this issue further, and discuss with your classmates the interaction between Batesian and Muellerian mimicry.

Effigy 10.19. A monarch (left) and a Viceroy butterfly (correct), long thought to exist a tasty mimic of the baneful Monarch butterfly. Recent enquiry has blurred this distinction.

 Photos: left, Jeff Mitton; right, Thomas G. Barnes/United states of america Fish and Wild fauna Service.

Sometimes animals defend themselves by imitating unsafe things. A number of caterpillars have developed an alarming resemblance to serpent heads. Perhaps the virtually realistic example of this is the Hemeroplanes caterpillar (also known equally a "viper worm"). When startled, it inflates its head and appears remarkably ophidian-similar (Figure 10.xx). The mimic octopus (see earlier description) comes to heed again. 42 When disturbed or in the presence of predators, this octopus is known to mimic other animals, such as sea snakes; tellingly, the animals it mimics are oft dangerous ones. Indeed, even superlative predators such as sea snakes might do good from imitating dangerous animals—in this case, imitating themselves. Despite their extremely toxic venom, they nonetheless are at risk from sharks and other large predators. When they forage and explore crevices, they must relax vigilance. During these times, they use both behavior and advent to ward off danger. In both color and pattern, the tail of the body of water snake Laticauda colubrine looks remarkably like to the head, especially from the side. When the snake is probing crevices, it slowly twists its tail, thus offering the appearance of the head to all comers. In this way, the bounding main ophidian mitigates the reduced vigilance that frequently accompanies foraging. 43

Figure 10.20. In addition to Hemeroplanes, other caterpillars such as this spicebush swallowtail (Papilio sp.) accept benefitted from looking like snakes.

 Photo: Ronald F. Billings, Texas Forest Service, Bugwood.org.

A rather dramatic octopus was recently discovered in a decidedly undramatic habitat. Indeed, the ordinary and fifty-fifty uniform appearance of the background (silt and sandy littoral areas near the mouths of rivers in Indonesia) may account for both the reason that the octopus remained undiscovered until 2001 and also the adaptive influences that cause the octopus'due south mimicry strategy to be so unusual. This mimic octopus (Thaumoctopus mimicus) mimics a variety of poisonous vertebrates, ranging from poisonous fish to sea snakes, maybe because cover-up against such a compatible groundwork might not be highly successful. (Exist ready to consider the miracle of mimicking unsafe animals later, in the context of deterrence.) In addition, nevertheless, when fleeing, this octopus can mimic a flounder, but then match its background (cover-up) when it stops, much like 1000. defilippi (run across Section x.2). Conspicuously, although predator avoidance strategies can be categorized for ease of organized give-and-take by humans, to the animal doing the predator avoidance, they blend together with remarkable effectiveness.

Mimicry extends beyond adopting another fauna'southward appearance. Some caterpillars look deceptively like bird droppings, others like twigs, leafhoppers may look more like leaves than similar insects, and a multifariousness of treehoppers mimic thorns. Perchance even more deceptive, some animals disguise parts of their bodies and so that they resemble other parts. 44 This beliefs is called diversion. For instance, some Lepidoptera (e.grand., Thecla togarna) have wing markings that look similar heads (complete with long "antennae") on the posterior parts of their wings. In that location is some contend nigh how redirecting attack benefits the prey, but the consensus is that the predator's attack is indeed redirected by such mimicry.

In lizards, tail-flicking may serve a similar diversionary purpose. In this case, the tail does non mimic any other role of the trunk, but because it moves more than the rest of the animal, it draws the predator's attention away from more vulnerable areas. If the tail is seized by the predator, the lizard can autotomize (break off) the tail and escape. 45,46 In at least one species of lizard, Acanthodactylus beershebensis, this diversion is correlated with ontogenetic changes in foraging beliefs. 47 Young (<3 weeks old) lizards are agile predators, moving almost more than older lizards and frequenting more than open up microhabitats. Because of this, young lizards probably expose themselves to predators more than older lizards do, which tend toward sit-and-wait foraging beliefs. The young lizards also have blueish tails, which they wiggle and wave more oft than adults do; the blue color of the tails fades with age, along with the wiggling and waving beliefs. Thus, conspicuous tail color, conspicuous tail movement, and conspicuous foraging habits are all common in young lizards, and not common in older lizards.

Even olfactory property mimicry is possible. It is idea that ground squirrels appoint in defensive smell mimicry when they chew rattlesnake skins that take been shed and then lick their fur. 48

Of Special Interest: Mass Overwintering by Snakes

Garter snakes (Thamnophis sirtalis parietalis) overwinter in dens. When they kickoff emerge, they are common cold and sluggish. In addition, emerging females are most immediately set upon by hordes (>100) of males in mating assurance. Emerging males may mimic females, producing a pheromone that is typical of a female. It was first thought that this behavior was a reproductive tactic that allowed the female-mimicking males (called she-males) increased admission to females. Further research with larger sample sizes and temperature-sensing devices revealed that this was a male strategy that could accept 2 benefits: protection from predators in the mating ball and faster posthibernation warm-up. The reproductive males seeking females take a body temperature of over 25°C; the ground is more than 15°C libation. Females that are the subject of male attention increase their body temperatures from 4°C to twenty°C in 30   min. Males in a similar situation receive like advantages. The she-male beliefs is transient and disappears as a she-male warms up. 49

Animals may fifty-fifty mimic a wounded and vulnerable version of themselves. Killdeers are well known for their "cleaved wing" displays. In this display, a parent bird, upon spotting a predator, will motility away from its nest, dragging an "injured" fly. It will practice this, continuing to move merely out of the predator's reach, until it is a safety distance from the nest; then information technology will fly away. The predator, in the meantime, has been lured away from the bird'south offspring (Figure ten.21).

Figure x.21. A killdeer feigning injury. The killdeer is well known for its broken-wing display; by pretending to exist hurt and unable to flee, it lures predators away from its nest—and then flies away.

 Photo: Tracy Thomas.

Finally, some animals go and then far in self-mimicking as to mimic their dead selves. This behavior is chosen thanatosis, from a Greek word meaning "a putting to death," and is mutual not but among insects but also vertebrates. Virginia opossums (Didelphis marsupialis) are perhaps near famous for this behavior and have given rise to the expression "playing possum," in reference to not only expiry-feigning, simply almost any kind of duplicity, especially that involving wellness. 50 The adaptive benefits of the behavior have been rigorously tested in flour beetles. Researchers selected two strains of Tribolium beetles for long and brusk death-feigning episodes, and showed that later ten generations of selection, which resulted in a clear thanatosis difference between the two lines, those selected for thanatosis were far more than likely to survive the attentions of a predatory spider. 51

Of Special Interest: Thanatosis in Shakespeare—The Better Function of Valor

Humans are among the vertebrates that occasionally feign expiry, and in the earth of theater, there are few death-feigning scenes more famous than that of Falstaff in Henry 4 Part I. After escaping almost certain decease past playing expressionless, Falstaff says that playing dead in club to alive is "no counterfeit." He then goes on to advise circumspection, speaking 1 of those many phrases from Shakespeare's work that has remained in employ in the English linguistic communication for hundreds of years:

To die is to be a counterfeit, for he is but the counterfeit of a human being who hath non the life of a man; but to counterfeit dying when a man thereby liveth, is to be no counterfeit, but the true and perfect image of life indeed. The better office of valor is discretion…. (Scene iv: 114–118)

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Darwin, Charles (Darwinism)

Michael T. Ghiselin , in Encyclopedia of Biodiversity (2d Edition), 2013

Early Darwinians

Given such a range of alternatives and the pocket-sized corporeality of research that had been done, it makes sense that from the outset there were few Darwinians other than Darwin himself. Because he was largely responsible for getting evolutionary thinking in general accepted by the intellectual community, a lot of evolutionists who did not take natural selection nonetheless considered themselves his followers. The degree to which Darwinism, in the sense that nosotros use that term hither, was a minority position has sometimes been exaggerated. We tin can place quite a number of important contemporaries of Darwin who established successful research programs based on the report of natural selection. Foremost among these of course was Alfred Russel Wallace (1832–1913), its codiscoverer. As well very distinguished was Wallace'due south traveling companion, Henry Walter Bates (1825–1892), the discoverer of Batesian mimicry. 2d only to Darwin in his mastery of the theory was Fritz Müller (1822–1897). He is best remembered for his discovery of Müllerian mimicry, but he besides was the first to propound the idea that developmental stages may restate evolutionary ones. Both Fritz Müller and his blood brother Hermann (1829–1883) conducted magisterial enquiry on pollination symbiosis under Darwin's influence. It is worth emphasizing that these scientists were outstanding for their performance as naturalists in the field. The kind of research that they did has been fundamental to our understanding of biodiversity because it documents how natural selection takes place in existent environments.

Darwin also had of import followers whose work was more focused in the museum and the laboratory. He had a close circle of followers, botanist Joseph Dalton Hooker (1817–1911), zoologists George John Romanes (1848–1894), and John Lubbock (1834–1913). In that location was also August Weismann (1834–1914), whose ideas near the continuity of the germplasm made natural choice seem a much more plausible explanation for evolution than Lamarckism. Neo-Darwinism is rightly associated with the proper noun of Weismann, whose basic position was that natural selection is not but the main but the exclusive evolutionary machinery. Really he admitted 2 small-scale ones that had been invoked by Darwin: sexual selection and pleiotropy.

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Population Genetics

Brian Charlesworth , in Encyclopedia of Biodiversity, 2001

Two.H.iii. The Evolution of Close Linkage

There are ii biologically important features of systems with strong epistatic selection. The get-go is that such selection may impose strong constraints on the degree of linkage between polymorphic loci. Suppose that the population is initially segregating for alleles A and a at one locus but is initially fixed for b at a 2nd locus. If a mutation B arises at this locus which interacts with the alleles at the first locus, such that AB is selectively favored only aB is disfavored, B may be unable to invade the population unless c is beneath some threshold value. But mutations at loci that are sufficiently closely linked to the start polymorphism in the organisation will be able to establish subsequent polymorphisms. This process has probably been of import in the evolution of some of the classic examples of supergenes (systems of very closely linked loci held in strong linkage disequilibrium by option), such as Batesian mimicry in butterflies ( Ford, 1975) and sex chromosomes. Similarly, if ab and AB are both fitter than Ab and aB, a population fixed for ab may only evolve a two-locus polymorphism if at that place is a double mutation to AB and if c is sufficiently small. This probably occurred in the evolution of meiotic drive systems, which require combinations of alleles at several loci that are individually disfavored.

Second, there is a selective reward to modifier alleles that reduce the frequency of genetic recombination betwixt the 2 loci once a two-locus polymorphism has been established. If suitable genetic variation in recombination rates is available, this volition eventually lead to such close linkage that the system has the appearance of a single locus (Fisher, 1930). This principle has wide generality; assay of the conditions for spread of rare modifiers of recombination rates has shown that randomly mating populations under epistatic selection generating linkage disequilibrium at a arrangement of loci will e'er tend to evolve closer linkage (Barton and Charlesworth, 1998). Since genetic recombination is a virtually-universal feature of living organisms, these findings have led to the search for situations that promote rather than repress recombination; these involve forces such as mutation and environmental change that perturb populations away from equilibria under choice (Barton and Charlesworth, 1998).

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