What is the accumulation of differences between species or populations?

Answer: Divergence evolution or divergent selection

Explanation:

The divergent evolution/divergent selection can be defined as the process of accumulation of differences between the related populations lies within the species. This process leads to speciation.

This occurs when the two populations of the same species get separated by a geographic barrier. The separated members of the same species experience different selective pressure that are responsible for adaptation in the new environment.