The Difference between Batesian and Mullerian mimicry
In any study of Biology, whether done in high school or college would be incomplete without a study of mimicry. The Encyclopaedia Britannica defines mimicry as:
“Mimicry, in biology, phenomenon characterized by the superficial resemblance of two or more organisms that are not closely related taxonomically. This resemblance confers an advantage—such as protection from predation—upon one or both organisms through some form of “information flow” that passes between the organisms and the animate agent of selection. The agent of selection (which may be, for example, a predator, a symbiont, or the host of a parasite, depending on the type of mimicry encountered) interacts directly with the similar organisms and is deceived by their similarity.” (Encyclopaedia Britannica 2000)
From the above definition, we can conclude that mimicry is the phenomenon of when an animal or plant resembles either another animal or inanimate object in order to gain any benefit attributed to the mimicked animal or object. Whether that is to pretend to be poisonous or inedible to a predator, or the complete opposite of a predator appearing harmless to prey. Studies into mimicry and how it is achieved in the natural world has formed an important field of study for evolutionary biologists for generations.
The following article will be dedicated to theories of mimicry that have formed the backbone of evolutionary studies. Those theories being Batesian mimicry and Mullerian mimicry. The difference between the two may seem subtle at first but with the help of examples occurring in the insect world, the difference will be made apparent.
The Encyclopaedia Britannica defines Batesian mimicry as:
“…a form of biological resemblance in which a noxious, or dangerous, organism (the model), equipped with a warning system such as conspicuous coloration, is mimicked by a harmless organism (the mimic). The mimic gains protection because predators mistake it for the model and leave it alone. This form of mimicry is named for its discoverer, the 19th-century English naturalist H.W. Bates.” (Encyclopaedia Britannica 1998)
To, labor the point, Batesian mimicry is where an unprotected prey species, or mimic, imitates a toxic or otherwise protected species, or model (Biodiversity Lab 2017). Initially, when Henry Bates posited the theory, after a trip to the Amazon where he discovered how a variety of butterfly species resembled an unpalatable species, Charles Darwin and Alfred Russel Wallace hailed the discovery as a fine example of natural selection. Work on Batesian mimicry continues to this day and scientists have a strong theoretical framework for providing evidence supporting the theory (Biodiversity Lab 2017). In fact, many of the studies into Batesian mimicry in Butterflies has become one of the strongest proof supporting evolutionary biology.
Nature is littered with examples of this. In Borneo, the grasshopper, Condylodera tricondyloides, so strongly resembles tiger beetles that it has often been mistaken as tiger beetles in many a museum collection. The tiger beetle is very aggressive and this is the trait the grasshopper hopes to imitate to help try to ensure its survival (Salvato 1997).
Often the example of the Monarch butterfly and the Viceroy butterfly is presented as an example of Batesian mimicry. In this instance, the Viceroy butterfly was thought to mimic the Monarch butterfly as the Monarch is unpalatable to predators. In fact, it was recently discovered that the Viceroy was just as unpalatable to predators, been mainly birds (Salvato 1997). Thus, rather than been an example of Batesian mimicry it is actually an example of Mullerian mimicry which will be discussed below.
Another example of true Batesian mimicry occurs with the ant-mimicking spider, Myrmarachne, which look striking similar to one of its predators the weaver ant, Oecophylla Smaragdina. If the spider did not resemble the ant so closely it would be surely swarmed and consumed by the ants.
Batesian mimicry can either be manifested in sexually monomorphic, polymorphic or sex-limited species (Biodiversity Labs 2017).
- Sexually monomorphic means that there is no difference between sexes of the same species other than their genitalia. They are similar in size and coloring.
- Polymorphic species are those that have different forms that arise from the same genotype, or genetic makeup. For example the differences in colors amongst South American Jaguars.
- Sex-limited mimicry means that a certain trait is only available to a certain sex of that species. Some butterfly species will exhibit Batesian mimicry only in the female and not the male. This means that the female will have the coloring, for instance, of a protected species while the male will not. Hence, the male will be targeted by predators and hopefully not the female. This would potentially assist the survival of the species (Biodiversity Lab 2017).
The Encyclopaedia Britannica defines Mullerian mimicry as:
“…a form of biological resemblance in which two or more unrelated noxious, or dangerous, organisms exhibit closely similar warning systems, such as the same pattern of bright colors. According to the widely accepted theory advanced in 1878 by the German naturalist Fritz Müller, this resemblance, although differing from the better-known Batesian mimicry (in which one organism is not noxious), should be considered mimicry nonetheless, because a predator that has learned to avoid an organism with a given warning system will avoid all similar organisms, thus making the resemblance a protective mechanism.” (Encyclopaedia Britannica 2009)
Put differently Mullerian mimicry describes the phenomenon seen in a number of dangerous or toxic species who come to exhibit similar colorings or other traits that facilitate predator learning. This would imply that the predator after trying to consume one species would avoid the other species displaying the same or similar coloring (Coyne 2017). Fritz Muller, after whom the theory is named, discovered this mimic pattern approximately twenty years after Henry Bates theorized Batesian mimicry (Hadley 2017).
In Mullerian mimicry, the species is both the model and the mimic unlike in Batesian mimicry where it can only either be the mimic or the model. Thus, in Mullerian mimicry, the various species are said to form “mimicry rings” in which unrelated species adopt certain colors or patterns indicating that it is toxic or whichever trait protects it from prey. In order for these mimicry rings to occur all the species involved in the ring must occur in the same geographical area (Coyne 2017).
An excellent example of this occurs amongst members of the Ampulicidae (cockroach wasp), Apidae (a type of bee), and Chrysididae (cuckoo wasp) who, although different species, have adapted the same metallic green color. They are all stinging insects, so the coloring would indicate to a bird they mimic rings unsuitableness as prey. If a bird were to try and eat one and realized that it could not, then it would in future all other species who resembled the first one.
As we have seen insects and animals, in general, have adapted varying methods to try and secure the survival of their species. In summary, Batesian mimicry occurs when an unprotected species, the mimic, imitates a protected species, the model, in order to make it seem like the unprotected species is indeed protected. Mullerian mimicry is where a set of different protected species adopt similar colorings to show potential predators that it is protected. In the example, we saw stinging insects displaying a similar color. Another example would be inedible butterflies displaying similar colorings and patterns.
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Biodiversity Lab, 2017. Research: Diversity and the Evolution of Batesian Mimicry. Retrieved from http://biodiversitylab.org/batesian-mimicry
Coyne, J. 2017. Müllerian mimicry in the Hymenoptera. Retrieved from https://whyevolutionistrue.wordpress.com/2017/01/29/mullerian-mimicry-in-the-hymenoptera/
Encyclopaedia Britannica, 1998. Batesian mimicry. Retrieved from https://global.britannica.com/science/Batesian-mimicry
Encyclopaedia Britannica, 2000. Mimicry. Retrieved from https://global.britannica.com/science/mimicry
Encyclopaedia Britannica, 2009. Mullerian mimicry. Retrieved from https://global.britannica.com/science/Mullerian-mimicry
Hadley, D. 2017. What is Mullerian mimicry? Retrieved from http://insects.about.com/od/Insect_Defenses/f/What-Is-Mullerian-Mimicry.htm
Salvato, M. 1997. Chapter 28: Most Spectacular Batesian Mimicry. Retrieved from http://entnemdept.ifas.ufl.edu/walker/Ufbir/chapters/chapter_28.shtml