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In evolutionary biology, convergent evolution describes the process whereby organisms not closely related independently evolve similar traits as they both adapt to similar environments. On a molecular level, this can happen due to random mutation unrelated to adaptive changes; see Long branch attraction.
In cultural evolution, convergent evolution is the development of similar cultural adaptations to similar environmental conditions by different peoples with different ancestral cultures.
An example of convergent evolution is the similar nature of the flight/wings of insects, birds, pterosaurs, and bats. All four serve the same function and are similar in structure, but each evolved independently. Some aspects of the lens of eyes also evolved independently in various animals.
Convergent evolution is similar to, but distinguishable from, the phenomena of evolutionary relay and parallel evolution. Evolutionary relay refers to independent species acquiring similar characteristics through their evolution in similar ecosystems, but not at the same time (e.g. dorsal fins of extinct ichthyosaurs and sharks). Parallel evolution occurs when two independent species evolve together at the same time in the same ecospace and acquire similar characteristics (extinct browsing-horses and extinct paleotheres).
Structures that are the result of convergent evolution are called analogous structures or homoplasies; they should be contrasted with homologous structures, which have a common origin.
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Animal Examples
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Several mammal groups have independently evolved prickly protrusions of the skin, called spines - Echidnas (Monotremes), Hedgehogs (insectivores), Old World porcupines (Rodents) and New World porcupines (a separate group of rodents). In this case, because the two groups of Porcupines are relatively closely related, they would be considered to be an example of parallel evolution; neither Echidnas nor Hedgehogs, however, are closely related to Rodents at all. In fact the last common ancestor of all four groups was a contemporary of the Dinosaurs.
Vultures come in two varieties as a result of convergent evolution: both Old World vultures and New World vultures eat carrion, but Old World vultures are in the eagle and hawk family and use eyesight for food discovery; the New World vultures are related to storks and use the sense of smell (as well as sight) to find carrion. In both cases they search for food by soaring, circle over carrion, and group in trees, and both have featherless necks.
The Neotropical poison dart frog and the Mantella of Madagascar have independently developed similar mechanisms for obtaining alkaloids from a diet of ants and storing the toxic chemicals in skin glands. They have also independently evolved similar bright skin colors that warn predators of their toxicity.
Assassin spiders are a group comprised of two lineages which evolved independently. They have very long necks, fangs larger in proportion than any other spider, and hunt other spiders by snagging them from a distance.
The smelling organs of the terrestrial coconut crab are similar to those of insects.
Koalas of Australasia have evolved fingerprints, very similar to those of humans.
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Plant examples
Prickles, thorns and spines are all modified plant tissues that have evolved to prevent or limit herbivory, these structures have evolved independently a number of times.
The aerial rootlets found in ivy (Hedera) are similar to those of the Climbing Hydrangea (Hydrangea petiolaris) and some other vines. These rootlets are not derived from a common ancestor but have the same function of clinging to whatever support is available.
Euphorbia and many Cactaceae species both occur in hot, dry environments (see picture below) and have similar modifications.
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Biochemical/Molecular examples
The existence of distinct families of carbonic anhydrase is believed to illustrate convergent evolution.
The use of (Z)-7-dodecen-1-yl acetate as a sex pheromone by the Asian elephant (Elephas maximus) and by >100 species of Lepidoptera.
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See also
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