There is an island in the middle of a large river that houses a large population of ants. Damming of the river causes the island to flood and only the highest points of the island are now above water. The ants cannot swim, so are now in multiple isolated populations. Which of the following best describes this event?

a. isolation by dispersal
b. isolation by vicariance
c. a form of sympatric speciation
d. a form of speciation due to continued gene flow
e. a form of speciation due to polyploidy

Option B, This situation represents isolation by vicariance.

Explanation:

Isolation by variance occurs when geographical barriers occur in a habitat that lead to unevenly distribution of population.  

Here in this case the dam on the river is a barrier to the stability of habitat (island) of ants

“Isolation by variance” differs from “isolation by dispersal” as in “isolation by dispersal”, the population of a given species crosses a barrier that already exists.

Hence, the correct answer is option B

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