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In its most basic form, coevolution is defined as evolution in two or more species brought about by reciprocal selective effects between those species . The term was introduced by Paul Ehrlich and Peter Raven in 1964 in their famous article Butterflies and plants: a study in coevolution (“ Butterflies and plants: a study on coevolution ”), in which they showed how various genera and families of butterflies depended on each other. of certain phylogenetic groups of plants for their food.
coevolutionary phenomena
One of the coevolutionary phenomena are sex and genetic recombination. These phenomena may have been caused by a coevolutionary “race” between organisms and their parasites. In this case, the rate of evolution and the probability of producing resistance to infection in hosts and virulence in parasites are enhanced by recombination.
Sexual selection is another phenomenon of coevolution between female choice potentiated by male secondary sexual traits. In this case, coevolution occurs within the same species, but it is still a type of coevolution.
Some studies include frequency-dependent selection between two types of players in an evolutionary “game.” The “game theory” underlying this idea may be between species as in interspecific competition, or within species (different morphs of the same species) competing for a resource such as food or females. Evolutionary interactions of this type also often produce coevolution.
Coevolution and interspecific interactions
Coevolution can occur in any interspecific interaction. For example:
- Interspecific competition for food or space.
- Parasite-host interactions.
- Predator/prey interactions.
- Symbiosis.
- Mutualisms.
However, close interspecific interactions do not always lead to coevolution. Mimicry, for example, can be a parasite-host interaction (in Batesian mimicry) or mutualism (Müllerian mimicry).
Mimicry is also a good example showing that coevolution is not always the result of interspecific interactions, because perhaps surprisingly, the result of this phenomenon almost always seems to be a unilateral adaptation of one species to another.
types of coevolution
The answer to the question “how likely is coevolution?” It depends on what is meant by coevolution. Several possibilities have been proposed:
specific coevolution
In specific coevolution or coevolution in the strict sense, one species closely interacts with another and changes in one species induce adaptive changes in the other, and vice versa. In some cases, this adaptation may be polygenic; in others, there may be gene-to-gene coevolution, in which mutual interactions occur between individual loci of the two species.
Specific coevolution can, of course, be short-lived, but if the interaction is very close, as is the case in many host-parasite systems, concordant speciation , or cospeciation , can occur, in which speciation in one form causes speciation in other.
Of course, cospeciation does not necessarily require coevolution. For example, a very minor but highly host-restricted parasite can species as long as its host is specific, without the parasite causing any evolutionary reaction in the host.
diffuse coevolution
In diffuse coevolution, also called guild coevolution, entire groups of species interact with other groups of species, resulting in changes that cannot truly be identified as examples of specific, pairwise coevolution between two species.
For example, a group of plant species can be fed by a certain family of insects, which in turn can change hosts frequently (in evolutionary time). Plants can develop defensive adaptations, both chemical and physical defenses, such as spines, that work against a large number of species. Over time, some of the insects may be able to overcome the plant’s defenses, leading to further evolution of the plant, and so on.
Escape and radiation coevolution
Another related type of evolution is called escape and radiation coevolution. In this case, an evolutionary innovation by either party to a coevolutionary interaction allows for adaptive radiation or speciation due to the availability of ecological opportunity.
Coevolutionary Competitive Interactions and Adaptive Radiation
This is an ecological principle known as the Gause principle . In it, related species must differ in some part of their ecology; that is, if two species have identical or nearly identical resources, competitive exclusion will occur and the less well-adapted species will go extinct.
If this is true, and it probably is, the reverse should also be true. If a species colonizes an area where there are no competitors, it can undergo ecological release and reach very large population sizes. And not only that, but colonists may also experience disruptive selection, followed by speciation. The process can be repeated in the case of multiple species, which evolve apart from each other to form an adaptive radiation.
Moreover, in addition to colonizing a new habitat, possession of a unique adaptation may also allow adaptive radiation to colonize a new “adaptive zone,” which opens as a result of adaptive radiation.
Sources
- Ehrlich, P.R and Raven, PH (1964). Butterflies and plants: a study in coevolution . Evolution 18 (4), 586-608.
- Schmitz, O. (2017). Functional predator-prey traits: understanding the adaptive machinery that drives predator-prey interactions .
