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Divergent evolution or divergent selection is the accumulation of differences between closely related populations within a species, leading to
speciation Speciation is the evolution Evolution is change in the Heredity, heritable Phenotypic trait, characteristics of biological populations over successive generations. These characteristics are the Gene expression, expressions of genes that are ...

speciation
. Divergent evolution is typically exhibited when two populations become separated by a geographic barrier (such as in
allopatric Allopatric speciation (from Ancient Greek ἄλλος, ''allos'', meaning "other", and πατρίς, ''patris'', "fatherland"), also referred to as geographic speciation, vicariant speciation, or its earlier name, the dumbbell model, is a mode of ...
or
peripatric speciation Peripatric speciation is a mode of speciation Speciation is the evolution Evolution is change in the Heredity, heritable Phenotypic trait, characteristics of biological populations over successive generations. These characteristics are t ...
) 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 (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 Evolutionary biology is the subfield of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular ...
of the
finches The true finches are small to medium-sized passerine birds in the family (biology), 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 wh ...

finches
of the
Galapagos
Galapagos
or the coloration differences in populations of a species that live in different habitats such as with pocket mice and
fence lizards
fence lizards
. The term can also be applied in
molecular evolution Molecular evolution is the process of change in the sequence composition of cellular molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings ...
, such as to
protein Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a No ...

protein
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 Molecular evolution is the process of change in the sequence composition of c ...
) 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 Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to their offspring; eit ...
arises when an
adaptation In , adaptation has three related meanings. Firstly, it is the dynamic evolutionary process that fits s to their environment, enhancing their . Secondly, it is a state reached by the population during that process. Thirdly, it is a or adapti ...

adaptation
has arisen independently, creating analogous structures 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 J. T. Gulick. 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 Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to their offspring; either through asexual reproduction or sexual reproduction, ...

evolution
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 Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a ...

kittiwake
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 always coupled with convergent evolution, 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 Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to their offspring; eit ...
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 parall ...
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 In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiver ...

Darwin's Finches
. 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 origin of the domestic dog The domestic dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated Domestication is a sustained multi-generational relationship in which one group of organisms assumes a significant de ...
and the modern
wolf The wolf (''Canis lupus''), also known as the gray wolf or grey wolf, is a large canine Canine may refer to: Zoology * dog-like mammals (i.e. members of the canid subfamily Caninae) ** ''Canis'', a genus including dogs, wolves, coyotes, a ...

wolf
. Dogs and wolves both diverged from a common ancestor. The similarity of the
mitochondrial DNA Mitochondrial DNA (mtDNA or mDNA) is the DNA Deoxyribonucleic acid (; DNA) is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five car ...

mitochondrial DNA
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 their strength and endurance to haul heavy freight as a sled dog A sled dog is a dog The domestic dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a ...

malamute
s and
huskies
huskies
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


See also

*
Cladistics Cladistics (; ) is an approach to biological classification In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular ...

Cladistics
*
Devolution Devolution is the statutory A statute is a formal written enactment of a legislature, legislative authority that governs the legal entities of a city, State (polity), state, or country by way of consent. Typically, statutes command or p ...
*
Chronospecies A chronospecies is a species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organ ...

Chronospecies


References


Further reading

* {{evo ecol Evolutionary biology Evolution of animals