Divergent evolution or divergent selection is the accumulation of differences between closely related populations within a species, leading to

speciation Speciation is the evolutionary process by which populations evolve to become distinct species. The biologist Orator F. Cook coined the term in 1906 for cladogenesis, the splitting of lineages, as opposed to anagenesis, phyletic evolution within ...

. Divergent evolution is typically exhibited when two populations become separated by a geographic barrier (such as in

allopatric Allopatric speciation () – also referred to as geographic speciation, vicariant speciation, or its earlier name the dumbbell model – is a mode of speciation that occurs when biological populations become geographically isolated from ...

peripatric speciation Peripatric speciation is a mode of speciation in which a new species is formed from an isolated peripheral population. Since peripatric speciation resembles allopatric speciation, in that populations are isolated and prevented from exchanging g ...

) and experience different selective pressures that drive adaptations to their new environment. After many generations and continual evolution, the populations become less able to interbreed with one another. The American naturalist

J. T. Gulick John Thomas Gulick (March 13, 1832 – April 14, 1923) was an American missionary and naturalist from Hawaii. He was one of the pioneers of modern evolutionary thinking based on his studies of Hawaiian snails of the genus '' Achatinella''. He wa ...

(1832–1923) was the first to use the term "divergent evolution", with its use becoming widespread in modern evolutionary literature. Classic examples of divergence in nature are the

adaptive radiation In evolutionary biology, adaptive radiation is a process in which organisms diversify rapidly from an ancestral species into a multitude of new forms, particularly when a change in the environment makes new resources available, alters biotic int ...

of the

finches The true finches are small to medium-sized passerine birds in the family Fringillidae. Finches have stout conical bills adapted for eating seeds and nuts and often have colourful plumage. They occupy a great range of habitats where they are usua ...

of the Galapagos or the coloration differences in populations of a species that live in different habitats such as with

pocket mice Perognathinae is a subfamily of rodents consisting of two genera of pocket mice. Most species live in complex burrows within the deserts and grasslands of western North America, They feed mostly on seeds and other plant parts, which they carry i ...

and fence lizards. The term can also be applied in

molecular evolution Molecular evolution is the process of change in the sequence composition of cellular molecules such as DNA, RNA, and proteins across generations. The field of molecular evolution uses principles of evolutionary biology and population genetics ...

, such as to

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

s that derive from homologous genes. Both orthologous genes (resulting from a speciation event) and paralogous genes (resulting from

gene duplication Gene duplication (or chromosomal duplication or gene amplification) is a major mechanism through which new genetic material is generated during molecular evolution. It can be defined as any duplication of a region of DNA that contains a gene. ...

) can illustrate divergent evolution. Through gene duplication, it is possible for divergent evolution to occur between two genes within a species. Similarities between species that have diverged are due to their common origin, so such similarities are homologies. In contrast,

convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...

arises when an

adaptation In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the po ...

has arisen independently, creating

analogous structures Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...

such as the wings of birds and of insects.

Creation, definition, and usage

The term divergent evolution is believed to have been first used by

. Divergent evolution is commonly defined as what occurs when two groups of the same species evolve different traits within those groups in order to accommodate for differing environmental and social pressures. Various examples of such pressures can include predation, food supplies, and competition for mates. The tympanal ears of certain nocturnal insects are believed to be a result of needing the ultrasonic hearing that tympanal ears provide in order to hear predators in the dark. Non-nocturnal insects - that do not need to fear nocturnal predators - are often found to lack these tympanal ears.

Causes

Animals undergo divergent

evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...

for a number of reasons. Predators or their absence, changes in the environment, and the time at which certain animals are most active are chief among them.

Predators

A lack of predators – predatory birds and mammals - for cliff-side nest residing

kittiwake The kittiwakes (genus ''Rissa'') are two closely related seabird species in the gull family Laridae, the black-legged kittiwake (''Rissa tridactyla'') and the red-legged kittiwake (''Rissa brevirostris''). The epithets "black-legged" and "red-le ...

caused that particular group of kittiwake to lose their ancestral mobbing behavior that had been exhibited up until that point for protecting young. The mobbing behavior normally displayed by the kittiwake is lost when the kittiwake take residence in this area with little threat from predators towards their young. The mobbing behavior was originally developed to protect ground-level nests containing young from various predators such as reptiles, mammals and other birds.

Environment

The cliff-side nesting area itself was similarly responsible for the kittiwakes losing their mobbing mentality – predatory mammals small enough to fit on the cliff edges along with the kittiwakes and their offspring would not be able to make the climb up while predatory birds would not be able to maneuver near the cliff face while also being afflicted by the weather conditions of the area.

Distinctions

Divergent evolution is understood in distinction to

, as they are both similar and different in various facets such as whether something evolves, what evolves, and why it evolves. It is instructive to compare divergent evolution with both convergent and parallel evolution.

Divergent versus convergent evolution

Convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...

is defined as a similar trait evolution that occurs in two otherwise different species of animal as a result of those two species living in similar environments with similar environmental pressures (like predators and food supply). It differs from divergent evolution in that the species involved are different while the traits they obtain do not differ from each other. An example of convergent evolution is the development of horns in various species for sparring over mates, resources, and territory

Divergent versus parallel evolution

Parallel evolution Parallel evolution is the similar development of a trait in distinct species that are not closely related, but share a similar original trait in response to similar evolutionary pressure.Zhang, J. and Kumar, S. 1997Detection of convergent and paral ...

is the development of a similar trait in species descending from the same ancestor. It is similar to divergent evolution in that the species descend from the same ancestor, but it differs in that the trait is the same while in divergent evolution the trait is not. An example of parallel evolution is that certain arboreal frog species, 'flying' frogs, in both Old World families and New World families, have developed the ability of gliding flight. They have "enlarged hands and feet, full webbing between all fingers and toes, lateral skin flaps on the arms and legs, and reduced weight per snout-vent length".

Darwin's Finches

One of the most famous examples of divergent evolution is the case of

Darwin's Finches Darwin's finches (also known as the Galápagos finches) are a group of about 18 species of passerine birds. They are well known for their remarkable diversity in beak form and function. They are often classified as the subfamily Geospizinae or t ...

. During Darwin's travels to the Galápagos Islands he discovered several different species of finch that shared a common ancestor. They lived on varying diets and had beaks that differed in shape and size reflecting their diet. The changes in beak shape and size were believed to be required to support their change in diet. Some Galápagos finches have larger and more powerful beaks to crack nuts with. A different type allows the bird to use cactus spines to spear insects in the bark of trees.

Divergent evolution in dogs

Another good example of divergent evolution is the

origin of the domestic dog The domestication of the dog was the process which created the domestic dog. This included the dog's genetic divergence from the wolf, its domestication, and the emergence of the first dogs. Genetic studies show that all ancient and modern dog ...

and the modern

wolf The wolf (''Canis lupus''; : wolves), also known as the gray wolf or grey wolf, is a large canine native to Eurasia and North America. More than thirty subspecies of ''Canis lupus'' have been recognized, and gray wolves, as popularly u ...

. Dogs and wolves both diverged from a common ancestor. The similarity of the

mitochondrial DNA Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial D ...

sequences from 162 wolves from various parts of the world and 140 dogs of 60 different breeds, revealed by genomic research, further supported the theory that dogs and wolves have diverged from shared ancestry. Dogs and wolves have similar body shape, skull size, and limb formation, further supporting their close genetic makeup and thus shared ancestry. For example,

malamute The Alaskan Malamute () is a large breed of dog that was originally bred for its strength and endurance to haul heavy freight as a sled dog and hound. It is similar to other arctic breeds such as the husky, the spitz, the Greenland Dog, Canad ...

s and

huskies Husky is a general term for a dog used in the polar regions, primarily and specifically for work as sled dogs. It refers to a traditional northern type, notable for its cold-weather tolerance and overall hardiness. Modern racing huskies that mai ...

are physically and behaviorally similar to wolves. Huskies and malamutes have very similar body size and skull shape. Huskies and wolves share similar coat patterns as well as tolerance to cold. In the hypothetical situations, mutations and breeding events were simulated to show the progression of the wolf behavior over ten generations. The results concluded that even though the last generation of the wolves were more docile and less aggressive, the temperament of the wolves fluctuated greatly from one generation to the next.Romanchik, J. 2011. From the Wild Wolf to Man’s Best Friend:An Analysis of a Hypothetical Wolf Population and the Change in Temperament, Possibly Leading to Their Domestication. Old Dominion University http://d2oqb2vjj999su.cloudfront.net/users/000/082/618/962/attachments/Scientific%20Paper-%20Wolves%20to%20Dogs.pdf