Convergent evolution

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. 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
 * The marsupial Thylacine and placental Canids.


 * The Flightless Cormorant of the Galapagos Islands, unlike other cormorants, now has wings developed for swimming rather than flight, equal in proportion to penguins.
 * Other
 * The similarities in diet and activity patterns between the thorny devil (Moloch horridus) and the Texas horned lizard (Phrynosoma cornutum) both in different clades.
 * Modern Crocodilians, and prehistoric phytosaurs, champsosaurs, and certain labyrinthodont amphibians. The resemblance between the crocodilians and phytosaurs in particular is quite striking.
 * 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–(by the opposite of crypsis, namely aposematism).
 * Assassin spiders are a group comprising two lineages that evolved independently. They have very long necks and fangs proportionately larger than those of 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.
 * The body shape of the prehistoric fish-like reptile Ophthalmosaurus and other ichthyosaurians, dolphins (aquatic mammals), and tuna (scombrid fish).
 * The brachiopods and bivalve molluscs, which both have very similar shells.

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

 * 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 more than 100 species of Lepidoptera.
 * The independent development of the catalytic triad in serine proteases independently with subtilisin in prokaryotes and the chymotrypsin clan in eukaryotes.
 * The repeated independent evolution of nylonase in two different strains of Flavobacterium and one strain of Pseudomonas.
 * The biosynthesis of plant hormones such as gibberellin and abscisic acid by different biochemical pathways in plants and fungi.