Reproductive Isolation: Definition, Types, Examples and Process

What Is Reproductive Isolation?

Scheidung describes those factors that make the species different and ensures that the individuals of one species do not interbreed with those of another species to produce viable offspring. This concept is essential in evolutionary biology since it assists in the identification of how new species develop and in the explanation of how variations of genes are retained across generations.

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This Story also Contains

1. What Is Reproductive Isolation?
2. Mechanisms Of Reproductive Isolation
3. Examples Of Reproductive Isolation In Nature
4. Role Of Reproductive Isolation In Speciation
5. Recommended video for "Reproductive Isolation"

There are several ways in which reproductive isolation can be presented such as pre-mating barriers where there is no possibility of the two featuring and or mating and post-mating barriers where there are reduced chances of the offspring germinating. Knowledge of these mechanisms gives information about the processes of formation of new species and the preservation of biotic diversity.

Mechanisms Of Reproductive Isolation

The mechanism of reproductive isolation includes the following:

Prezygotic Barriers

These barriers include:

Habitat Isolation

This applies that habitat isolation exists when species occupy different geographical areas and therefore they cannot meet for breeding. For example, the eastern garter snake and the western garter snake live in different kinds of surroundings, which decreases the option for the two species to mate.

Temporal Isolation

Cases of temporal separation result in species breeding at different periods of the year and thus do not get to mate. For example, the American toad and the Fowler’s toad are sympatric, but the former breeds in spring while the latter breeds in summer.

Behavioural Isolation

The mating isolation involves elements of functionality that would in one way or the other render the two species incapable of interbreeding. For instance, hymns or ballets use calls or relatively specific dances, especially for birds of the peacock kind that are special to the species.

Mechanical Isolation

Mechanical isolation is when distinct physical obstacles hinder the potential copulatory from successful mating. For example, the organs of reproduction of two different species of insects might not mesh in the slightest and therefore, copulation is out of question.

Gametic Isolation

Mutual impotence is the condition in which the sperm of one species cannot meet and fertilize the egg of the other or a related species. For example, sea urchins are broadcast spawners and the sperm will not be able to behave as sperm from another species because of molecular recognition events.

Postzygotic Barriers

These barriers include the following:

Reduced Hybrid Viability

Diminished heterosis involves some form of follows or low survival of hybrids (offspring of two different species). For instance, a crossbreed between Rana catesbeiana and Rana clamitans most of the time their offsprings fail to reach maturity. This barrier also contributes to avoiding the occurrence of hybrid offspring in future generations.

Reduced Hybrid Fertility

Low-hybrid fertility is the term used when hybrids are … or are inclined to be wholly or partially sterile. A relative example is a mule which is a cross between a horse male and a donkey female and is always infertile and cannot procreate. Of the mentioned effects, this one specifically bars the hybrids from being able to reproduce and even go to the next generations.

Hybrid Breakdown

Hybrid breakdown on the other hand happens when the first generation hybrids are viable as well as fertile, but their second generation is inviable or sterile. For example, in rice, the hybrids between two species are themselves oftentimes fertile but the offspring have low viability and/or fertility. This barrier effectively prevents the interbreeding of two species across generations because the aforesaid types of hybrids are less fit.

Examples Of Reproductive Isolation In Nature

The examples are listed below-

Darwin's Finches

The famous case of reproductive isolation driving the process of speciation is that of Darwin’s finches of the Galápagos Islands. For instance, various species of finches developed different mechanisms and sizes of beakers about the island food resource base that was available. These differences in the beak structure and songs are examples of prezygotic isolations whereby no two species can interbreed for even if the female lays her eggs in the male’s nest, they will not hatch, thus showing how geographic and behavioural barriers play a significant role in forging new species.

Eastern and Western Meadowlarks

The two species that seem closely related are the Eastern and Western meadowlarks but they are reproductively isolated through prezygotic isolation mainly by the disharmonizing sounds. Despite the ranges and contact calls often overlapping, there appear to be species-specific calls used in mate selection which help to reduce cases of interbreeding. This behavioural isolation is for species perseverance since only individuals with the same mating calls reproduce.

Lions and Tigers (Ligers and Tigons)

Lions and tigers can't be in the same pride since lions are larger than tigers However, ligers are obtained where a male lion mates with a tiger female and tigons come from a tiger male and a lion female. These hybrids are often feasible but crop up with the problem of low fecundity. A liger is bigger than the parent species, but it cannot mate due to infertility, which is inherited from the lion's mother. This example sheds light on the fact that though there are occasional hybrids, postzygotic barriers such as problems with fertility prevent the two species from interbreeding and thus remain distinct.

Role Of Reproductive Isolation In Speciation

Speciation requires reproductive isolation, as it prevents gene flow among populations that may result in new species through means other than evolution.

Allopatric Speciation

• Allopatric speciation is the process by which new species are formed because of the geographical isolation of the populations.

• Physical barriers include factors that hinder the movement of genes from one population to another for instance mountains or rivers.

Sympatric Speciation

• Sympatric speciation is the kind of speciation that takes place with no geographical isolation but might be through ecological opportunities and sexual selection.

• For instance, variation in mating preference or sources of food may cause the formation of new species.

Parapatric Speciation

• In parapatric speciation, populations are situated near each other, but the two groups interact very little due to some barriers.

• Lower gene exchange results in new species at the boundaries of various geographic populations.

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