Meaning of Coevolution
Coevolution is the name given to the process by which two or more species evolve simultaneously in response to selective pressures exerted by the other.
This process may explain why some species are co -adaptive , i.e. mutually adapted, as occurs in pollinating insects and flowers .
Coadaptations can arise through processes other than coevolution. Two strains can evolve independently and pre-adapt before establishing a relationship.
Therefore, adaptations alone are not enough to ensure that coevolution has occurred. To ensure that this process will take place, it would be necessary to show that the ancestors of the coadapted forms evolved together, which is quite complex to do.
Other evidence that can help support the occurrence of coevolution may come from comparisons with related species.
Co-evolution of two taxa can give rise to cophylogenies, which are phylogenies that have virtually the same branching pattern.
But it is important to emphasize: not all cophylogeny can be explained by coevolution and coevolution does not always result in cophylogeny.
Congruence in the phylogenies of two taxa can occur by sequential evolution, when changes in one taxon lead to changes in the other, but without the reciprocal, or even without the taxa interacting with each other, by allopathic speciation .
Furthermore, there are cases where coevolution does not result in the formation of phylogenetic groups . An example is what seems to have happened to butterflies and plants.
Each butterfly family feeds on a restricted range of plants, which are generally not closely related phylogenetically, but produce the same type of chemical defense.
The likely explanation is that these insects may have developed mechanisms to detoxify compounds produced by a certain type of plant, opening up opportunities to explore other chemically similar plants.
Insects and Flowers
Still thinking about the insect-plant relationship, the existing adaptations between pollinating insects and flowers are probably the result of coevolution .
A flower may hold its nectar in a place that restricts its access by insects with long tongues. Insects that have specialized adaptations for a particular type of flower will likely seek only flowers of the same type.
This is beneficial for the plant, since it favors the dispersion of its pollen to other flowers of the same species, as well as to insects, which suffer little competition.
Natural selection may favor flowers that keep their nectar in ever deeper places and insects with ever longer tongues.
But coevolution doesn’t always promote mutual benefit. In other cases, this process is antagonistic, that is, while one party benefits, the other suffers some damage.
When parasites and hosts , ecological competitors, or predators and prey evolve with each other, if one of the opposite does not develop some adaptation in response to its antagonist, it may become extinct.
Therefore, antagonistic co -evolution can lead to the extinction of one of the parties or to an equilibrium that can be static (the species reaches a set of optimal conditions and remains there) or dynamic , known as the “ Red Queen ”.
In the Red Queen mode, natural selection acts continuously and alternatively in each species, in successive responses to the adaptations developed by the antagonistic species.
This leads to a kind of arms race in which species develop more and more powerful adaptations.