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Author: Michael Schiff
Biological studies today are done under a lens of the theory of evolution by natural selection. This means that populations change over time because the ratios of specific genes within individuals change through time as the environment around that population changes, and that these changes make the individuals in the population better able, in some way, to pass their genes on to the next generation. This leads to the understanding that most genes that are actually expressed in a given individual should generally be adaptive to that individual’s environment because the maladaptive genes would have been outperformed by the adaptive ones through time. Traits can be adaptive in two general ways: either by A) directly increasing the organism’s reproductive success or B) increasing its survivability, which generally leads to an increase in reproductive success. Mimicry is most often adaptive in the latter sense, i.e. that it increases the individual’s chance to survive long enough to reproduce one or more times. For example, a bull snake looking like a rattlesnake increases its survivability because predators are less likely to eat something that looks like a venomous rattlesnake. There is seemingly a contradiction here though, as many forms of mimicry make the organism more susceptible to predation via loud colors or conspicuous displays, such as a king snake mimicking a coral snake. So why should mimicry have evolved in the first place?
The System: There are many species of coral snakes and similarly colored/patterned snakes throughout the tropical and temperate parts of North and South America. Several are extremely venomous, some mildly venomous, and many are non-venomous.
The Story: When Batesian mimicry was first described, coral snakes and their supposed mimics were often used as seemingly obvious examples. Many non-venomous species seem to suffer less predation due to having similarly colored bands along their bodies as do true coral snakes. However, as more research was performed, the system showed itself to be more complex. In 1878, Fritz Muller suggested another type of mimicry system, Mullerian mimicry (Wickler 1968). This mimicry is basically the same idea as Batesian mimicry except that it extends to mutual mimicry of different venomous species. In short, multiple dangerous species mutually benefit by mimicking each other because it gives each individual less chance of being a "mistake" a predator attacks before learning not to attack species with that pattern because they are venomous. This seemed to apply readily to coral snakes because several of their mimics are also venomous. But then herpetologist Robert Mertens came along and suggested that this is still partly incorrect because the true coral snakes have such potent venom that would-be predators would not survive a defensive bite. Therefore he suggested that it is actually the mildly venomous snakes that are being mimicked by both the true coral snakes and the non-venomous species. This was later labeled as Mertensian mimicry It should however also be noted that many newer studies suggest the similar patterns and coloration of these species to be due to similar environmental factors, not mimicry at all (Herrera, Smith,&Chiszar 1981), and that predators may not avoid true coral snakes at all (Beckers , Leenders&Strijbosch 1996a).
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