The correct answer to this open question is the following.
It seems that ypur question is incomplete because it doesn't include any context, reference, map, or something we can use to help you answer the question.
What tribes are you referring to? What is the time in history?
However, trying to help you, we can comment on the following.
We assume that you are referring to the European presence in Africa after the Berlin Conference of 1855. If that is the case, then we can say that what happened to tribes when the Europeans made these new borders was that they eliminate some borders, modified others, create new regions, moved tribes from their former territories, and displaced people.
This was a moment in history known as the Scramble for Africa," that started in 1885 and ended approximately in 1914.
The European countries involved in the partition of Africa were France, Great Britain, Portugal, Germany, Italy, Spain, and Belgium. In reality, these countries were only interested in colonizing Africa to exploit the many raw materials and natural resources of the continent.