Final: Mimicry (and camouflage) and its evolution

This discussion topic submitted by Allison Rossetti (rossetam@miamioh.edu) at 6:33 pm on 6/8/99. Additions were last made on Wednesday, May 7, 2014.

Mimicry, one of several anti-predatory devices, is very important in nature throughout the whole world. The most well-known example of mimicry is probably the viceroy butterfly mimicing the monarch. However I chose to focus my topic of mimicry to only species in the Neotropics. I intend to emphasize how mimicry is important for survival. If an non-dangerous organism can trick its predator into thinking that it is dangerous, the predator will most likely avoid it and that organism has succeeded in remaining alive. As years progress, species become better and better at this trickery, which leads to natural selection. Evolution is simply a series of minor changes.

A. Mimicry-predators are unable to distingusish one organism from another

1. Batesian-one organism is warning colored and the other is not
-models must outnumber mimics for mimicry to be successful
-discovered by Bates in 1862 by watching butterflies

2. Mullerian-both species are poisonous, the mimic is just less
-mutualistic relationship
-discovered by Fritz Muller in 1879
-example: papilionid Batis Polydamus butterfly and B. beflus
varus on the Caribbean coast of Costa Rica

3. Mertensian-most offensive species is not the model because it is too
dangerous to allow predators to learn (it kills the predator)
and instead it is the mimic of the less offensive species
(coral snakes)

-best examples of mimicry occur in the tropics
-occur in birds, fish, snakes, amphibians, moths, beetles, bugs, flies, snails, butterflies

B. Ants

1. insects and spiders resemble them because ants sting and bite
-they act fidgety and busy, mimicing the ant's behavior which allows it
into the ant's nest
-spiders put their fourth pair of legs forward to look like antennae
-also have a constricted waist

2. immature stages of grasshoppers, stick insects, and aphids mimic ants
-aphids rear end looks like the head of an ant, moves its hind legs
like antennae

3. 80 species of rove beetles live in ant's nests and resemble them in color
and shape, chemical mimicry is used so they can enter the nests

4. chemical mimicry also allows ants into termites' nest

C. Beetles

1.commonly orange and black suggesting warning
-insects (wasps, moths, sawflies, other beetles) mimic this coloration
because of reflex bleeding
-reflex bleeding--produce blood from joints

2. tropical celyphid flies inflate their thorax to look like a beetle

3. some beetles even feed on other beetles that do reflex bleeding in order
to become more dangerous

D. Butterflies
- are able to look alike and belong to a different family
- in tropics, difficult to identify a butterfly by color or pattern

1. in Central America, 40 species of Heliconius which are all dangerous to
predators and make birds sick

- 11 distinct races of H. melpomene that are different, for every
local H. melpomene, there is a H. erato mimic

2. Mimicry complex- butterflies exist at different intervals in the forest
- this occurs because these are the heights predators have a hard
time distinguishing them because of the light penetration

3. Gene protection-in order for a predator to discover a nasty butterfly,
one must be eaten, therefore after offspring is
produced, one parent is eaten in order to stop the
predator from eating its offspring

-butterflies are beautifully colored so predators can remember them
-colors also exist so species can recognize each other and mate

E. Others that mimic
-snakes
-sabre-toothed blenny mimics sea swallows (cleaner fish) and takes a bite
from the bigger fish--this is aggressive mimicry

F. Camouflage- resemblance of inanimate objects like stones and bird droppings
- katydids look like twig
- disruptive coloration - overlook the outline of the animal
because of patches blending (military)
- sloth with algae
- Great Potoo - looks like dead wood (Central America)

G. Evolution
- a mimic realized that a slight change was advantageous and with time,
the change improved by natural selection

1. requirements-
a. predators learn to discriminate and remember bad experiences
b. mimic resemblance is inherited and color patterns are under
genetic control--research has found that mimicry is controlled
by 1 or 2 genes

2. in Costa Rica, researchers altered the pattern of Heliconois and sent
them into the forest, Fewer of the altered species were found later
- predators will more likely eat a species poorly mimicing another
leading to natural selection

Sources:

Mimicry in Plants and Animals by Wolfgang Wickler
McGraw-Hill Book Company, 1968

Animal Camouflage by Adolf Portmann
University of Michigan Press, 1959

Camouflage and Mimicry by Denis Owen
University of Chicago Press, 1980

Patterns of Survival by Lorus and Margery Milne
Prentice-Hall, Inc., 1967

The Neotropical Companion by John Kricher
Princeton University Press, 1997 p. 159-162

"Mimicry: Sheep in wolves' clothing" by Graeme D. Ruxton
Nature, August 27, 1998 p. 833-834

www.tulane.edu/~guill/adaptation.html#Mimicry
www.pbs.org/tal/costa_rica/res2/tricking.html

For Further Info on this Topic, Check out this WWW Site: http://fig.cox.miami.edu/Faculty/Tom/bil160/18_mimicry.html.
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