Answer:
Allopatric speciation
Step-by-step explanation:
The kind of speciation that occurs when 2 populations of rabbits separated by water become different species is allopatric speciation.
Allopatric speciation occurs when two populations of the same organisms become physically separated and each population ends up developing unique characteristics that make them distinct species. This is as opposed to sympatric speciation in which a new species just spontaneously emerge from the existing population without any being separated from the population.
Other forms of speciations include parapatric speciation which occurs as a result of the spreading out of a population over a large geographical area and peripatric speciation which occurs as a result of the breaking off of a small group from a large group of organism.
In the illustration, the two populations of rabbits are separated physically by the river. Hence, the speciation that will occur if each population goes ahead to form a new species would be allopatric speciation.