In
evolutionary biology
Evolutionary biology is the subfield of biology that studies the evolutionary processes (natural selection, common descent, speciation) that produced the diversity of life on Earth. It is also defined as the study of the history of life fo ...
, an evolutionary arms race is an ongoing struggle between
competing sets of
co-evolving
In biology, coevolution occurs when two or more species reciprocally affect each other's evolution through the process of natural selection. The term sometimes is used for two traits in the same species affecting each other's evolution, as well ...
gene
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...
s,
phenotypic
In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological proper ...
and
behavioral
Behavior (American English) or behaviour (British English) is the range of actions and mannerisms made by individuals, organisms, systems or artificial entities in some environment. These systems can include other systems or organisms as well ...
traits that develop escalating
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 ...
s and counter-adaptations against each other, resembling an
arms race
An arms race occurs when two or more groups compete in military superiority. It consists of a competition between two or more states to have superior armed forces; a competition concerning production of weapons, the growth of a military, and t ...
. These are often described as examples of
positive feedback
Positive feedback (exacerbating feedback, self-reinforcing feedback) is a process that occurs in a feedback loop which exacerbates the effects of a small disturbance. That is, the effects of a perturbation on a system include an increase in the ...
.
[Dawkins, R. 1996. '']The Blind Watchmaker
''The Blind Watchmaker: Why the Evidence of Evolution Reveals a Universe without Design'' is a 1986 book by Richard Dawkins, in which the author presents an explanation of, and argument for, the theory of evolution by means of natural selecti ...
'' New York: W. W. Norton. Note: This book was also published by Penguin in 1991. While the text is identical, page numbers differ The co-evolving gene sets may be in different species, as in an evolutionary arms race between a
predator
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...
species and its
prey
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the ...
(Vermeij, 1987), or a
parasite
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...
and its
host
A host is a person responsible for guests at an event or for providing hospitality during it.
Host may also refer to:
Places
* Host, Pennsylvania, a village in Berks County
People
*Jim Host (born 1937), American businessman
* Michel Host ...
. Alternatively, the arms race may be between members of the same species, as in the manipulation/sales resistance model of communication (Dawkins & Krebs, 1979) or as in
runaway evolution
Fisherian runaway or runaway selection is a sexual selection mechanism proposed by the mathematical biologist Ronald Fisher in the early 20th century, to account for the evolution of ostentatious male ornamentation by persistent, directional fe ...
or
Red Queen effects. One example of an evolutionary arms race is in
sexual conflict
Sexual conflict or sexual antagonism occurs when the two sexes have conflicting optimal fitness strategies concerning reproduction, particularly over the mode and frequency of mating, potentially leading to an evolutionary arms race between ma ...
between the sexes, often described with the term
Fisherian runaway
Fisherian runaway or runaway selection is a sexual selection mechanism proposed by the mathematical biologist Ronald Fisher in the early 20th century, to account for the evolution of ostentatious male ornamentation by persistent, directional fem ...
.
Thierry Lodé
Thierry Lodé (born 1956 in Tarbes) is a French biologist and professor of evolutionary ecology in a CNRS lab at the University of Rennes 1.
His work deals mainly with sexual conflict
Sexual conflict or sexual antagonism occurs when the two ...
emphasized the role of such antagonistic interactions in
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 ...
leading to
character displacement
Character displacement is the phenomenon where differences among similar species whose distributions overlap geographically are accentuated in regions where the species co-occur, but are minimized or lost where the species' distributions do not o ...
s and
antagonistic coevolution Sexual antagonistic co-evolution is the relationship between males and females where sexual morphology changes over time to counteract the opposite's sex traits to achieve the maximum reproductive success. This has been compared to an arms race b ...
.
Symmetrical versus asymmetrical arms races
Arms races may be classified as either symmetrical or asymmetrical. In a symmetrical arms race, selection pressure acts on participants in the same direction. An example of this is trees growing taller as a result of competition for light, where the selective advantage for either species is increased height. An asymmetrical arms race involves contrasting selection pressures, such as the case of cheetahs and gazelles, where cheetahs evolve to be better at hunting and killing while gazelles evolve not to hunt and kill, but rather to evade capture.
Hostparasite dynamic
Selective pressure between two species can include
host-parasite coevolution. This antagonistic relationship leads to the necessity for the pathogen to have the best virulent alleles to infect the organism and for the host to have the best resistant alleles to survive parasitism. As a consequence, allele frequencies vary through time depending on the size of virulent and resistant populations (fluctuation of genetic selection pressure) and generation time (mutation rate) where some genotypes are preferentially selected thanks to the individual fitness gain. Genetic change accumulation in both populations explains a constant adaptation to have lower fitness costs and avoid extinction in accordance with the
Red Queen's hypothesis
The Red Queen hypothesis is a hypothesis in evolutionary biology proposed in 1973, that species must constantly adapt, evolve, and proliferate in order to survive while pitted against ever-evolving opposing species. The hypothesis was intended ...
suggested by
Leigh Van Valen
Leigh Van Valen (August 12, 1935 – October 16, 2010) was a U.S. evolutionary biologist. At the time of his death, he was professor emeritus in the Department of Ecology and Evolution at the University of Chicago. Research and interests
Amongs ...
in 1973.
Examples
The ''Phytophthora infestans''/Bintje potato interaction
![Plants certifiés Bintje](https://upload.wikimedia.org/wikipedia/commons/d/d4/Plants_certifi%C3%A9s_Bintje.png)
The
Bintje
Bintje is a middle-early ripening potato variety bred in the Netherlands by the Frisian schoolmaster K.L. de Vries in 1904 from (Munstersen x Fransen) and marketed for the first time in 1910. The name of the potato, a diminutive of Benedict, was ...
potato is derived from a cross between ''Munstersen'' and ''Fransen'' potato varieties. It was created in the Netherlands in the early 20th century and now is mainly cultivated in the North of France and Belgium. The oomycete ''Phytophthora infestans'' is responsible for the potato blight, in particular during the European famine in 1840.
Zoospore
A zoospore is a motile asexual spore that uses a flagellum for locomotion. Also called a swarm spore, these spores are created by some protists, bacteria, and fungi to propagate themselves.
Diversity Flagella types
Zoospores may possess one or ...
s (mobile spores, characteristics of oomycetes) are liberated by zoosporangia provided from a mycelium and brought by rain or wind before infecting tubers and leaves. Black colours appear on the plant because of the infection of its cellular system necessary for the multiplication of the oomycete infectious population. The parasite contains virulent-avirulent allelic combinations in several microsatellite loci, likewise the host contains several multiloci resistance genes (or
R gene
Resistance genes (R-Genes) are genes in plant genomes that convey plant disease resistance against pathogens by producing R proteins. The main class of R-genes consist of a nucleotide binding domain (NB) and a leucine rich repeat (LRR) dom ...
). That interaction is called
gene-for-gene relationship
The gene-for-gene relationship was discovered by Harold Henry Flor who was working with rust (''Melampsora lini'') of flax ('' Linum usitatissimum''). Flor showed that the inheritance of both resistance in the host and parasite ability to cause d ...
and is, in general, widespread in plant diseases. Expression of genetic patterns in the two species is a combination of resistance and virulence characteristics in order to have the best survival rate.
Bats and moths
Bat
Bats are mammals of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most ...
s have evolved to use echolocation to detect and catch their prey.
Moths
Moths are a paraphyletic group of insects that includes all members of the order Lepidoptera that are not butterflies, with moths making up the vast majority of the order. There are thought to be approximately 160,000 species of moth, many of w ...
have in turn evolved to detect the echolocation calls of hunting bats, and evoke evasive flight maneuvers,
or reply with their own ultrasonic clicks to confuse the bat's echolocation.
The
Arctiidae
The Arctiinae (formerly called the family Arctiidae) are a large and diverse subfamily of moths with around 11,000 species found all over the world, including 6,000 neotropical species.Scoble, MJ. (1995). ''The Lepidoptera: Form, Function and D ...
subfamily of Noctuid moths uniquely respond to bat echolocation in three prevailing hypotheses: startle, sonar jamming, and acoustic aposematic defense.
All these differences depend on specific environmental settings and the type of echolocation call; however, these hypotheses are not mutually exclusive and can be used by the same moth for defense.
The different defense mechanisms have been shown to be directly responsive to bat echolocation through
sympatry
In biology, two related species or populations are considered sympatric when they exist in the same geographic area and thus frequently encounter one another. An initially interbreeding population that splits into two or more distinct species sh ...
studies. In places with spatial or temporal isolation between bats and their prey, the moth species hearing mechanism tends to regress. Fullard et al. (2004) compared adventive and endemic Noctiid moth species in a bat-free habitat to ultrasound and found that all of the adventive species reacted to the ultrasound by slowing their flight times, while only one of the endemic species reacted to the ultrasound signal, indicating a loss of hearing over time in the endemic population.
However, the degree of loss or regression depends on the amount of evolutionary time and whether or not the moth species has developed secondary uses for hearing.
Some bats are known to use clicks at frequencies above or below moths' hearing ranges.
This is known as the allotonic frequency hypothesis. It argues that the auditory systems in moths have driven their bat predators to use higher or lower frequency echolocation to circumvent the moth hearing.
Barbastelle
''Barbastella'' is a genus of vespertilionid bats. There are seven extant species in this genus and one only known from fossil remains.
Species
The genus consists of the following species:
* ''Barbastella barbastellus'' – western barbastelle
...
bats have evolved to use a quieter mode of echolocation, calling at a reduced volume and further reducing the volume of their clicks as they close in on prey moths.
The lower volume of clicks reduces the effective successful hunting range, but results in a significantly higher number of moths caught than other, louder bat species.
Moths have further evolved the ability to discriminate between high and low echolocation click rates, which indicates whether the bat has just detected their presence or is actively pursuing them.
This allows them to decide whether or not defensive ultrasonic clicks are worth the time and energy expenditure.
The rough-skinned newt and the common garter snake
Rough-skinned newt
The rough-skinned newt or roughskin newt (''Taricha granulosa'') is a North American newt known for the strong toxin exuded from its skin.
Appearance
A stocky newt with rounded snout, it ranges from light brown to olive or brownish-black on ...
s have skin glands that contain a powerful nerve poison,
tetrodotoxin
Tetrodotoxin (TTX) is a potent neurotoxin. Its name derives from Tetraodontiformes, an order that includes pufferfish, porcupinefish, ocean sunfish, and triggerfish; several of these species carry the toxin. Although tetrodotoxin was discovere ...
, as an
anti-predator adaptation
Anti-predator adaptations are mechanisms developed through evolution that assist prey organisms in their constant struggle against predators. Throughout the animal kingdom, adaptations have evolved for every stage of this struggle, namely by avo ...
. Throughout much of the newt's range, the
common garter snake
The common garter snake (''Thamnophis sirtalis'') is a species of thamnophis snake, in the natricine subfamily, which is indigenous to North America and found widely across the continent. Most common garter snakes have a pattern of yellow strip ...
is resistant to the toxin. While in principle the toxin binds to a tube-shaped protein that acts as a sodium channel in the snake's nerve cells, a mutation in several snake populations configures the protein in such a way as to hamper or prevent binding of the toxin, conferring resistance. In turn, resistance creates a selective pressure that favors newts that produce more toxin. That in its turn imposes a selective pressure favoring snakes with mutations conferring even greater resistance. This evolutionary arms race has resulted in the newts producing levels of toxin far in excess of that needed to kill any other predator.
In populations where garter snakes and newts live together, higher levels of tetrodotoxin and resistance to it are observed in the two species respectively. Where the species are separated, the toxin levels and resistance are lower.
While isolated garter snakes have lower resistance, they still demonstrate an ability to resist low levels of the toxin, suggesting an ancestral predisposition to tetrodotoxin resistance. The lower levels of resistance in separated populations suggest a fitness cost of both toxin production and resistance. Snakes with high levels of tetrodotoxin resistance crawl more slowly than isolated populations of snakes, making them more vulnerable to predation.
[ The same pattern is seen in isolated populations of newts, which have less toxin in their skin. There are geographic hotspots where levels of tetrodotoxin and resistance are extremely high, showing a close interaction between newts and snakes.][
]
Predator whelk and the hard-shelled bivalve prey
The whelk
Whelk (also known as scungilli) is a common name applied to various kinds of sea snail. Although a number of whelks are relatively large and are in the family Buccinidae (the true whelks), the word ''whelk'' is also applied to some other marin ...
predators used their own shell to open the shell of their prey, oftentimes breaking both shells of the predator and prey in the process. This led to the fitness of larger-shelled prey to be higher and then more selected for through generations, however, the predator’s population selected for those who were more efficient at opening the larger-shelled prey. This example is an excellent example of asymmetrical arms race because while the prey is evolving a physical trait, the predators are adapting in a much different way.
Floodplain death adders and separate species of frogs
Floodplain death adders eat three types of frogs: one nontoxic, one producing mucus when taken by the predator, and the highly toxic frogs, however, the snakes have also found if they wait to consume their toxic prey the potency decreases. In this specific case, the asymmetry enabled the snakes to overcome the chemical defenses of the toxic frogs after their death. The results of the study showed that the snake became accustomed to the differences in the frogs by their hold and release timing, always holding the nontoxic, while always releasing the highly toxic frogs, with the frogs that discharge mucus somewhere in between. The snakes would also spend generously more time gaped between the release of the highly toxic frogs than the short gaped time between the release of the frogs that discharge mucus. Therefore, the snakes have a much higher advantage of being able to cope with the different frogs defensive mechanisms, while the frogs could eventually increase the potency of their toxic knowing the snakes would adapt to that change as well, such as the snakes having venom themselves for the initial attack. The coevolution is still highly asymmetrical because of the advantage the predators have over their prey.
Introduced species
When a species has not been subject to an arms race previously, it may be at a severe disadvantage and face extinction
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
well before it could ever hope to adapt to a new predator, competitor, etc. This should not seem surprising, as one species may have been in evolutionary struggles for millions of years while the other might never have faced such pressures. This is a common problem in isolated ecosystems such as Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
or the Hawaiian Islands
The Hawaiian Islands ( haw, Nā Mokupuni o Hawai‘i) are an archipelago of eight major islands, several atolls, and numerous smaller islets in the North Pacific Ocean, extending some from the island of Hawaii in the south to northernmost Kur ...
. In Australia, many invasive species
An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...
, such as cane toad
The cane toad (''Rhinella marina''), also known as the giant neotropical toad or marine toad, is a large, terrestrial true toad native to South and mainland Central America, but which has been introduced to various islands throughout Oceania ...
s and rabbit
Rabbits, also known as bunnies or bunny rabbits, are small mammals in the family Leporidae (which also contains the hares) of the order Lagomorpha (which also contains the pikas). ''Oryctolagus cuniculus'' includes the European rabbit speci ...
s, have spread rapidly due to a lack of competition and a lack of adaptations to cane toad bufotenine
Bufotenin (5-HO-DMT, bufotenine) is a tryptamine derivative - more specifically, a DMT derivative - related to the neurotransmitter serotonin. It is an alkaloid found in some species of toads (especially the skin), mushrooms and plants.
The nam ...
on the part of potential predators. Introduced species
An introduced species, alien species, exotic species, adventive species, immigrant species, foreign species, non-indigenous species, or non-native species is a species living outside its native distributional range, but which has arrived there ...
are a major reason why some indigenous
Indigenous may refer to:
*Indigenous peoples
*Indigenous (ecology), presence in a region as the result of only natural processes, with no human intervention
*Indigenous (band), an American blues-rock band
*Indigenous (horse), a Hong Kong racehorse ...
species become endangered
An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inva ...
or even extinct
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
, as was the case with the dodo
The dodo (''Raphus cucullatus'') is an extinct flightless bird that was endemic to the island of Mauritius, which is east of Madagascar in the Indian Ocean. The dodo's closest genetic relative was the also-extinct Rodrigues solitaire. The ...
.
See also
*Anti-predator adaptation
Anti-predator adaptations are mechanisms developed through evolution that assist prey organisms in their constant struggle against predators. Throughout the animal kingdom, adaptations have evolved for every stage of this struggle, namely by avo ...
*Parasite
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...
–host
A host is a person responsible for guests at an event or for providing hospitality during it.
Host may also refer to:
Places
* Host, Pennsylvania, a village in Berks County
People
*Jim Host (born 1937), American businessman
* Michel Host ...
interactions
*Parent–offspring conflict
Parent–offspring conflict (POC) is an expression coined in 1974 by Robert Trivers. It is used to describe the evolutionary conflict arising from differences in optimal parental investment (PI) in an offspring from the standpoint of the parent an ...
*Antimicrobial resistance
Antimicrobial resistance (AMR) occurs when microbes evolve mechanisms that protect them from the effects of antimicrobials. All classes of microbes can evolve resistance. Fungi evolve antifungal resistance. Viruses evolve antiviral resistance. P ...
References
General
*Dawkins, Richard
Richard Dawkins (born 26 March 1941) is a British evolutionary biologist and author. He is an emeritus fellow of New College, Oxford and was Professor for Public Understanding of Science in the University of Oxford from 1995 to 2008. An at ...
& Krebs, John R. (1979). Arms races between and within species. ''Proceedings of the Royal society of London'', B 205:489-511.
*{{cite journal , last1=Conner , first1=W. E. , last2=Corcoran , first2=A. J. , year=2012 , title=Sound strategies: the 65-million-year-old battle between bats and insects , journal=Annual Review of Entomology , volume=57 , pages=21–39 , doi=10.1146/annurev-ento-121510-133537 , pmid=21888517
External links
Nature's Eternal Arms Race (PBS Documentary)
Arms race
An arms race occurs when two or more groups compete in military superiority. It consists of a competition between two or more states to have superior armed forces; a competition concerning production of weapons, the growth of a military, and t ...
Arms race
An arms race occurs when two or more groups compete in military superiority. It consists of a competition between two or more states to have superior armed forces; a competition concerning production of weapons, the growth of a military, and t ...