In separate marshes, small populations of three species occur: grass fish, which disperse only in extreme rains and have an average dispersal of 1 individual every 45 generations, swamp rats, which occasionally disperse over land, averaging 2 individuals dispersing per generation, and marsh birds, which regularly fly from marsh to marsh, so that dispersal is extremely high. Assuming that the three species are equally common, the least genetic variation within populations would be expected in: Group of answer choices

The question is incomplete as it does not have the option which are:

a.  Grass fish, since they have the least gene flow, and gene flow acts to decrease genetic variation among populations.

b.  Swamp rats, since they will have the best balance between genetic drift and gene flow, resulting in high genetic variation among populations.

c.  Grass fish, since they are the best adapted to their aquatic environment, and adaptation increases genetic variation among populations.

d.  Marsh birds, since they have the highest level of gene flow, and gene flow increases genetic variation among populations.

e.  It is not possible to compare relative amounts of genetic variation among such different kinds of animals.

Option-A

Explanation:

The genetic variations are introduced in a population when the new combination of gene interact with each other and again a new combination of genes are formed.  

This genetic variation is possible when the flow of gene takes place that is the individuals are dispersed to another place.

In the given population, since it has been mentioned that the gene flow of Grass fish was very low because the probability of gene flow was 1 out of 45. Thus, the gene flow was very less, therefore, the less genetic variation is introduced in population.

Thus, Option-A is correct.

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