What is the Difference Between Dispersal and Vicariance?

Dispersal and vicariance are two biogeographic processes that cause the disjunct distribution of populations. They both lead to the isolation of a population by a geographic barrier, but they differ in the way the separation occurs:

• Dispersal: This process involves the migration of a part of a population across a preexisting geographical barrier. It is an active process in which organisms actively change their distributions by moving to new geographical areas. Dispersal can lead to the formation of new species as gene flow between the isolated populations becomes improbable, and the differences between their alleles become more pronounced.
• Vicariance: In contrast, vicariance occurs when a new geographical barrier appears, dividing the population. This barrier may be due to natural events such as the formation of a new lake, mountains, or other geographical features. As a result, gene flow between the populations on either side of the barrier is limited or completely prevented, leading to the differentiation of distinct but related species.

In summary, the main difference between dispersal and vicariance lies in the way the geographic separation occurs. Dispersal is the active migration of organisms across preexisting barriers, while vicariance involves the appearance of a new geographical barrier that divides the population. Both processes can lead to allopatric speciation, where a single species gives rise to multiple new species due to geographical isolation.

Comparative Table: Dispersal vs Vicariance

The main difference between dispersal and vicariance lies in the way populations become separated and the type of speciation they lead to. Here is a table comparing the two processes:

In summary, dispersal involves the movement of organisms to new locations, while vicariance involves the division of a population by a geographical barrier. Dispersal typically leads to allopatric speciation, whereas vicariance can lead to sympatric speciation.