Once two populations have been sufficiently reproductively isolated, microevolut

Question

Once two populations have been sufficiently reproductively isolated, microevolutionary processes act to further separate them genetically. This is why reproductive isolation can eventually lead to genetic isolation. When geographic barriers separate two populations that eventually form two separate species, we call this allopatric speciation. Allopatric speciation can happen through two mechanisms, dispersal and colonization or vicariance. Please define these mechanisms in your own words and give one example of each. Does genetic drift have a greater impact on species that have been formed through dispersal and colonization or vicariance? Why?

Explanation / Answer

6. Allopatric speciation can take place through dispersal and colonization or due to vacariance.

Allopatric speciation due to colonization and dispersal occurs when individuals of a population move to a new habitat or environment which is also known as founder effect. As a result of adaptation to the new environment, the isolated population faces genetic mutations due to which it becomes phenotypically and genotypically different from the original population.Thus in case of colonization and dispersal the isolated population becomes genetically distinct from the original population.

Example : diversification among Hawaiian Drososphila

In case of allopatric speciation due to vacariance a group of individuals gets seperated from the original population due to a geographcal barrier.These geographical barriers can be formation of a mountain range, river formation, formation of a canyon.

Example of vacariance is the isthmus of Panama, which is a land bridge that developed between North and South America.

7. Genetic drift will have more impact on population formed through colonization because in case of colonization small number of individuals are seperated from the origial population. Genetic drift acts more on smaller populations therefore population resulting due to colonization is more affected by genetic drift.

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