por What is ecological insulation?
He ecological insulation It is a mechanism that prevents reproductive crossing between two species that could produce hybrid offspring. A hybrid descendant is the result of the mixture of two individuals of different species, and it is sterile (that is, it cannot reproduce).
For example, the mule or mule is a hybrid animal that originates as a result of crossing a donkey (Equus africanus asinus) with a mare (Equus ferus caballus). This animal shares some traits with both parent species.
Also, the hinnies is a hybrid species that results from the crossing of a donkey with a horse. Mules and hinnies have different genes. The mule is a stronger and larger animal than the hinnies, and both are almost always sterile. In the rare cases of fertility in mules and hinnies, the young are weak and very underweight, with little chance of survival.
Another example is the cebroid or zebrallo, which is the individual resulting from the cross between a mare and a male zebra, and like most hybrids, it is sterile. Its appearance is like that of a horse, with the difference of the showy stripes, characteristic of zebras.
There are 5 ecological isolation processes that fulfill the function of preventing two different species from having hybrid or mixed offspring: ecological isolation, temporary isolation, behavioral isolation, spatial isolation, and mechanical/chemical isolation.
Ecological isolation mechanism
Ecological, or habitat, isolation is one of the 5 reproductive isolation mechanisms that prevent interbreeding between different species, prior to the formation of the zygote or egg (prezygotic isolation mechanism).
This mechanism occurs when two species that could genetically interbreed have reproductive barriers because they live in different areas. This is how different populations can occupy the same territory but live in different habitats, and therefore do not physically meet each other.
In addition to the other isolation mechanisms, ecological isolation prevents the production of hybrid species that do not favor the growth and development of biological populations, since most hybrid individuals are sterile, that is, incapable of reproducing.
Species involved in hybrid intercrossing are considered to have unsuccessful energy expenditure. Additionally, these reproductive isolation mechanisms play a crucial selective role in speciation.
Speciation is the process by which new species are formed. The speciation process is the one that has originated the diversity of organisms or biological diversity.
Examples of ecological insulation
Several examples of ecological insulation are cited below.
Ecological isolation in mammals
In India there is the tiger (Panthera tigris) and the lion (Panthera leo), two species of the same family (Felidae), which have the ability to interbreed.
However, the tiger lives in the jungle and the lion in the grasslands of the northeast of the country. Since the two species live in different habitats, their physical encounter does not occur. Each species, both the lion and the tiger, are isolated in their own spaces.
Ecological isolation in insects
The group Anopheles maculipennis It consists of 6 species of mosquitoes, some of which are associated with the transmission of malaria. Although these 6 species are very similar and indistinguishable morphologically, they can rarely produce hybrids, because they are isolated for reproduction and interbreeding, partly because they reproduce in different habitats.
While some species of Anopheles maculipennis they reproduce in brackish waters, others do it in fresh waters. Among the species that mate in freshwater, there are some that do so in running water and others that prefer stagnant water.
Ecological isolation in birds
One of the most cited examples of ecological isolation is the case of two closely related birds of the genus Turdus, like the common blackbird or thrush (Turdus merula), and the white-capped blackbird (Turdus torquatus).
The population of T. merulaa species that inhabits timberland areas of forests and urban gardens, is ecologically isolated from the T. torquatus, a species that reproduces in high mountain areas. Therefore, the chances of these species producing a hybrid is practically zero.
Ecological isolation in amphibians
Reproductive ecological isolation is also observed in different species of frogs. One of the many examples of this case is found in North America.
In North America, the population of the northern red-legged frog (aurora frog) is isolated from the American bullfrog population (catesbeian frog), since the former mates in ephemeral, fast-moving water currents, and the latter does so in permanent pools or pools.
In Australia, the crucifix frog (notaden bennettii) and the desert tree frog (Litoria rubella) They are found in desert environments. However, it is highly unlikely that they will mate, as the Crucifix Frog lives underground and only moves to the surface when it rains, while the Desert Tree Frog is an arboreal species.
Ecological isolation in fish
Another interesting example of this type of ecological reproductive isolation is seen in sticklebacks of the family Gasterosteidae. These fish have an elongated and thin body (fusiform), with 2 to 16 spines on their dorsal area and lack scales, although some species have a kind of bony plate armor.
While freshwater fish species Gasterosteidae live in running waters year-round, marine species found in the sea in winter migrate in spring and summer to river estuaries to mate.
In this case, the factor that acts as a reproductive barrier that prevents the two groups from interbreeding is adaptation to different salt concentrations.
Ecological isolation in plants
Another example of ecological isolation occurs in the case of the two species of spider plants in the genus Tradescantiathe Ohio spider plant (tradescantia ohiensis) and the zigzag spider plant (Tradescantia subaspera).
Both plants live in common geographical areas, but are unable to cross due to the difference in habitats. The T. ohiensis grows in sunny areas, while the T. subaspera prefers shady areas with little sun.
Additionally, these plants flower at different times of the year, that is, they also present temporary isolation.
We can conclude that in ecological isolation, the separation of groups of organisms occurs as a result of changes in their ecology or changes in the environment in which they live.
References
Ecological Speciation – an overview. Retrieved from sciencedirect.com.
Genetics and ecological speciation. Retrieved from pnas.org.