A population of snails lives in a large field. As the size of the population grows, individual organisms on one side of the field stop mating with individuals from the opposite side. Which of the following statements is true?

Over time, genetic differences between individual snails will increase.
Over time, genetic differences between individual snails will decrease.
The snail population will eventually split in two and evolve side by side in cospeciation.
This is an example of an increase in gene flow.