Even both terms are very similar, there is a difference. A dispersal event occurs when an initial specie travels from one place to another and due to the environmental factors and the adaptation that need to develop to survive will change into different species. In the other hand, the vicariance, is a process in which there is a specie and it lives in a wide are, but it fragments into groups mainly by the continental drift, so with the passing of time it turns into different characteristics, as the human race.
