Convergent evolution

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In evolutionary biology, convergent evolution is the process whereby organisms not closely related (not monophyletic), independently evolve similar traits as a result of having to adapt to similar environments or ecological niches[1]. It is the opposite of divergent evolution, where related species evolve different traits. 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. The striking similarities between hummingbird moths and hummingbirds is another example of convergent evolution.

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.

Animal examples

Mammals
  • 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.
  • Cat-like, sabre-toothed predators evolved in three distinct lineages of mammals — sabre-toothed cats, Nimravids (false sabre-tooths), and the marsupial thylacosmilids. Gorgonopsids and creodonts also developed long canines, but that is the only physical similarity.
  • A number of mammals have developed claws and long, sticky tongues that allow them to open the homes of social insects (e.g. ants and termites) and eat them. These include the four species of anteater, about 20 species of armadillo, eight species of pangolin, the African aardvark, four species of echidna, and the Australian numbat.
  • Koalas of Australasia have evolved fingerprints, very similar to those of humans. The Australian honey possum has developed a long tongue for taking nectar from flowers, the same sort of structure that butterflies possess to accomplish the same task.
Avian and Non-avian Dinosaurs
Other

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.
  • Many Euphorbia and Cactaceae species occur in hot, dry environments and have similar modifications (see picture below).

Examples for convergent evolution of enzymes and biochemical pathways

References

  1. Online Biology Glossary
  2. Tudzynski B. (2005). "Gibberellin biosynthesis in fungi: genes, enzymes, evolution, and impact on biotechnology". Appl Microbiol Biotechnol. 66: 597-611. PMID 15578178.
  3. Siewers V, Smedsgaard J, Tudzynski P. (2004). "The P450 monooxygenase BcABA1 is essential for abscisic acid biosynthesis in Botrytis cinerea.". Appl Environ. Microbiol. 70: 3868-3876. PMID 15240257.

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