https://en.wikipedia.org/wiki/Red_Queen_hypothesis
The Red Queen hypothesis (also referred to as Red Queen's, the Red Queen effect, Red Queen's race, Red Queen dynamics) is an evolutionary hypothesis which proposes that organisms must constantly adapt, evolve, and proliferate in order to survive while pitted against ever-evolving opposing organisms in a constantly changing environment, as well as to gain reproductive advantage.
The hypothesis intends to explain two different phenomena: the constant extinction rates as observed in the paleontological record caused by co-evolution between competing species, and the advantage of sexual reproduction (as opposed to asexual reproduction) at the level of individuals.
The Red Queen hypothesis (also referred to as Red Queen's, the Red Queen effect, Red Queen's race, Red Queen dynamics) is an evolutionary hypothesis which proposes that organisms must constantly adapt, evolve, and proliferate in order to survive while pitted against ever-evolving opposing organisms in a constantly changing environment, as well as to gain reproductive advantage.
The hypothesis intends to explain two different phenomena: the constant extinction rates as observed in the paleontological record caused by co-evolution between competing species, and the advantage of sexual reproduction (as opposed to asexual reproduction) at the level of individuals.
Origin
Leigh Van Valen proposed the hypothesis as an "explanatory tangent" to explain the "Law of Extinction" (known as Van Valen's law):
by showing that in many populations, the probability of extinction does
not depend on the lifetime of the population, instead being constant
over millions of years for a given population. This could be explained
by the coevolution
of species, where established species have evolved cooperatively by
assuming adaptive coevolutionary dependencies. These complementary
relationships develop through graduated symbiosis, directing punctuated advantages specialized enough to ensure a greater survivability and fitness rate for both species. Indeed, an adaptation in a population of one species (e.g. predators, parasites) may change the natural selection pressure on a population of another species (e.g. prey, hosts), giving rise to common antagonistic coevolutions. If this positive feedback occurs reciprocally, a potential dynamic coevolution may result.
The phenomenon's name is derived from a statement that the Red Queen made to Alice in Lewis Carroll's Through the Looking-Glass in her explanation of the nature of Looking-Glass Land:
Now, here, you see, it takes all the running you can do, to keep in the same place.
Van Valen coined the hypothesis "Red Queen" because under this
interpretation, populations have to "run" or evolve in order to stay in
the same place, or else go extinct.
Leigh Van Valen (1973) proposed the metaphor of an evolutionary arms race, which was appropriate for the description of biological processes with dynamics similar to arms races. In respective processes, an adaptation in a population of one species (e.g., predators, parasites) may change the selection pressure on a population of another species (e.g., prey, host), giving rise to an antagonistic coevolution.
The
Red Queen at the genus level: The linear relationship between survival
times and the logarithm of the number of genera suggests that the
probability of extinction is constant over time. Redrawn from Leigh Van Valen (1973).
The Red Queen hypothesis is used independently by Hartung and Bell to explain the evolution of sex, by John Jaenike to explain the maintenance of sex and W. D. Hamilton to explain the role of sex in response to parasites. In all cases, sexual reproduction confers species variability and a faster generational response to selection
by making offspring genetically unique. Sexual species are able to
improve their genotype in changing conditions. Consequently,
co-evolutionary interactions, between host and parasite, for example,
may select for sexual reproduction in hosts in order to reduce the risk of infection. Oscillations in genotype frequencies are observed between parasites and hosts in an antagonistic coevolutionary way
without necessitating changes to the phenotype. In multi-host and
multi-parasite coevolution, the Red Queen dynamics could affect what
host and parasite types will become dominant or rare.
Van Valen proposed the Red Queen hypothesis as an explanatory
tangent to his proposed "Law of Extinction" (also 1973), which he
derived from observation of constant probabilities of extinction within families of organisms across geological time.
Put differently, Van Valen found that the ability of a family of
organisms to survive does not improve over time, and that the lack of
correlation between age and extinction is suggestive of a random
process.
The Red Queen hypothesis as formulated by Van Valen provides a
conceptual underpinning to discussions of evolutionary arms races, even
though a direct test
of the hypothesis remains elusive, particularly at the
macroevolutionary level. This concept remains similar to that of a
system obeying a self-organized criticality.
For example, because every improvement in one species will lead to a selective
advantage for that species, variation will normally continuously lead
to increases in fitness in one species or another. However, since
different species tend to co-evolve, an improvement in one species
implies that it will get a competitive advantage over the other species,
and thus be able to capture a larger share of the resources available
to all. This means that the fitness increase in one evolutionary system
will tend to lead to the fitness decrease in another system. The only
way that a species involved in a competition for resources can maintain its fitness relative to other competing species is by improving its specific fitness. (From Heylighen, 2000)
The most obvious example of this effect are the "arms races" between predators
and prey (e.g., Vermeij, 1987), where the only way predators can
compensate for a better defense by the prey (e.g., rabbits running
faster than the previous generation]) is by developing a better offense
(e.g. foxes running faster than their predecessors). In this case, we
might consider the relative improvements (rabbits running faster than
foxes or vice versa) to be also absolute improvements in fitness. (From
Heylighen, 2000)
Discussions of sex and reproduction
were not part of Van Valen's Red Queen hypothesis, which addressed
evolution at scales above the species level. The microevolutionary
version of the Red Queen hypothesis was proposed by Bell (1982), also
citing Lewis Carroll, but not citing Van Valen .
Application to human conflict
One
can apply such arms races to human conflict and interpret them as a
prominent cause of conflict. According to Azar Gat, the Red Queen effect
arises when two competing groups find themselves in a security dilemma.
The security dilemma results when a group takes defensive measures
(which possess inherent offensive capabilities) to improve their
security, triggering a military arms race. This arms race, much like the
example previously referenced, causes each side to consume ever
increasing amounts of resources in order to outpace the other and to
gain an advantage. If an advantage is gained, the arms race is over and
the group with more resources has won. However, typically both sides
continue to match each other stride for stride, thus triggering the Red
Queen effect, as no matter how many resources each side invests, neither
is able to gain an advantage. The situation somewhat resembles the prisoner's dilemma.
Neither side can stop the arms race, due to mutual suspicion and fears
that the other group will gain a significant tactical advantage. Because
of this, the Red Queen effect is a common outcome of inter-human
competition and conflict.
Interspecies arms race
Predator-prey
relationship between rabbits and foxes following the principle of the
Red Queen hypothesis. The rabbit evolves increasing its speed to escape
the attack of the fox, and the fox evolves increasing its speed to reach
the rabbit. This evolution is constant, in case one of the two stops
evolving, its extinction will occur.
- A number of predator/prey couple where the weapon involved is the running speed.
"The rabbit runs faster than the fox, because the rabbit is running for his life while the fox is only running for his dinner." Aesop
The predator-prey relationship can also be established in the
microbial world, producing the same evolutionary phenomenon that occurs
in the case of foxes and rabbits. A recently observed example has as
protagonists M.xanthus (predator) and E.coli
(prey) in which a parallel evolution of both species can be observed
through genomic and phenotypic modifications, producing in future
generations a better adaptation of one of the species that is
counteracted by the evolution of the other, thus generating an arms race
that can only be stopped by the extinction of one of the species.
- The interactions between parasitoid wasps and insect larvae, necessary for the parasitic wasp's life cycle, are also a good illustration of an arms race. Indeed, some evolutionary strategy was found by both partners to respond to the pressure generated by the mutual association of lineages. For example, the parasitoid wasp group, Campoletis sonorensis, is able to fight against the immune system of its hosts, Heliothis virescens (Lepidopteran) with the association of a polydnavirus (PDV) (Campoletis sonorensis PDV). During the oviposition process, the parasitoid transmits the virus (CsPDV) to the insect larva. The CsPDV will alter the physiology, growth and development of the infected insect larvae to the benefit of the parasitoid.
Evidence
Evidence
for this explanation for the evolution of sex is provided by the
comparison of the rate of molecular evolution of genes for kinases and immunoglobulins in the immune system with genes coding other proteins. The genes coding for immune system proteins evolve considerably faster.
Further evidence for the Red Queen hypothesis was provided by
observing long‐term dynamics and parasite coevolution in a mixed sexual
and asexual population of snails (Potamopyrgus antipodarum).
The number of sexuals, the number of asexuals, and the rates of
parasite infection for both were monitored. It was found that clones
that were plentiful at the beginning of the study became more
susceptible to parasites over time. As parasite infections increased,
the once-plentiful clones dwindled dramatically in number. Some clonal
types disappeared entirely. Meanwhile, sexual snail populations remained
much more stable over time.
In 2011, researchers used the microscopic roundworm Caenorhabditis elegans as a host and the pathogenic bacterium Serratia marcescens
to generate a host–parasite coevolutionary system in a controlled
environment, allowing them to conduct more than 70 evolution experiments
testing the Red Queen hypothesis. They genetically manipulated the
mating system of C. elegans, causing populations to mate either
sexually, by self-fertilization, or a mixture of both within the same
population. Then they exposed those populations to the S. marcescens parasite. It was found that the self-fertilizing populations of C. elegans
were rapidly driven extinct by the coevolving parasites, while sex
allowed populations to keep pace with their parasites, a result
consistent with the Red Queen hypothesis.
Currently, there is no consensus among biologists on the main
selective forces maintaining sex. The competing models to explain the
adaptive function of sex have been reviewed by Birdsell and Wills.
Studies
The
influence of heterogeneity in species genomes has been recognized and
studied since the time of Darwin (1876) in the areas of heterosis
(hybrid vigor), inbreeding and genetic deterioration, operating on the
theory that lessening of the choice of gene variants and of potential
cooperation among different gene types limits the capabilities of the
restricted organism. Resultant genetic drift or genetic isolates reduce available corresponding genetic material volumes, where variable limitations can catalyze a consequential population bottleneck.
A study published in 2013 in Science
which examined the history of groups of extinct mammals illustrates the
failure to adapt and evolve new species when confronted by a
deteriorating environment. An interesting insight can be obtained from physical research.
The paradox of sex: The cost of males
Science writer Matt Ridley popularized the term in connection with sexual selection in his 1993 book The Red Queen, in which he discussed the debate in theoretical biology over the adaptive benefit of sexual reproduction
to those species in which it appears. The connection of the Red Queen
to this debate arises from the fact that the traditionally accepted Vicar of Bray hypothesis only showed adaptive benefit at the level of the species or group, not at the level of the gene (although the protean "Vicar of Bray" adaptation is very useful to some species that belong to the lower levels of the food chain). By contrast, a Red-Queen-type thesis suggesting that organisms are running cyclic arms races with their parasites
can explain the utility of sexual reproduction at the level of the gene
by positing that the role of sex is to preserve genes that are
currently disadvantageous, but that will become advantageous against the
background of a likely future population of parasites.
Further evidence of the Red Queen hypothesis was observed in
allelic effects under sexual selection. The Red Queen Hypothesis leads
to the understanding that allelic recombination is advantageous for
populations that engage in aggressive biotic interactions, such as
predator-prey or parasite-host interactions. In cases of parasite-host
relations, sexual reproduction can quicken the production of new
multi-locus genotypes allowing the host to escape parasites that have
adapted to the prior generations of typical hosts.
Mutational effects can be represented by models to describe how
recombination through sexual reproduction can be advantageous. According
to the mutational deterministic hypothesis, if the deleterious mutation
rate is high, and if those mutations interact to cause a general
decline in organismal fitness, then sexual reproduction provides an
advantage over asexually reproducing organisms by allowing populations
to eliminate the deleterious mutations not only more rapidly, but also
most effectively. Recombination is one of the fundamental means that explain why many organisms have evolved to reproduce sexually.
Sexual organisms must spend resources to find mates. In the case of sexual dimorphism,
usually one of the sexes contributes more to the survival of their
offspring (usually the mother). In such cases, the only adaptive benefit
of having a second sex is the possibility of sexual selection, by which organisms can improve their genotype.
Evolution of aging
The Red Queen hypothesis has been also invoked by some authors to explain evolution of aging.
The main idea is that aging is favored by natural selection since it
allows faster adaptation to changing conditions, especially in order to
keep pace with the evolution of pathogens, predators and prey.
Court jester hypothesis
A competing evolutionary idea is the court jester hypothesis, which indicates that an arms race is not the driving force of evolution on a large scale, but rather it is abiotic factors.
Black Queen Hypothesis
The Black Queen Hypothesis is a theory of reductive evolution that suggests natural selection can drive organisms to reduce their genome size.
In other words, a gene that confers a vital biological function can
become dispensable for an individual organism if its community members
express that gene in a "leaky" fashion. Like the Red Queen Hypothesis,
the Black Queen Hypothesis is a theory of co-evolution.
