Difference Between Dispersal and Vicariance

The key difference between dispersal and vicariance is that dispersal is the migration of a part of the population into new areas across a preexisting geographic barrier while vicariance is the division of the population due to the appearance of a new geographical barrier.

Disjunct distribution is the separation of related taxonomic groups into different geographic areas. These geographically discontinuous patterns of population occur due to two main events : dispersal and vicariance. Dispersal is the migration of taxa into different geographic areas across preexisting geographical barriers such as mountain chain. In contrast, vacariance is the separation of taxonomic groups due to the appearance of new geographic barriers such as oceans, mountains, etc. However, both processes result in the isolation of a population by a geographic barrier.

1. Overview and Key Difference
2. What is Dispersal
3. What is Vicariance
4. Similarities Between Dispersal and Vicariance
5. Side by Side Comparison – Dispersal vs Vicariance in Tabular Form
6. Summary

What is Dispersal?

Dispersal is the migration of a part of the population into new geographical areas, passing preexisting geographical barriers. Therefore, members of a group of organisms separate from each other by geographical barriers and show geographically discontinuous distribution patterns due to dispersal. This isolation of a population may result differentiation of a new taxon with time due to allopatric speciation.

Difference Between Dispersal and Vicariance

Figure 01: Allopatric Speciation

What is Vicariance?

Vicariance is an explanation for the geographically discontinuous distribution of species. Moreover, it is the primary model of alollpatric speciation. In vicariance, division of the members of a population takes place due to the appearance of a new geographical barrier. Thus, they separate by a new geographical barrier. Earlier, they were distributed widely. Now due to the emergence of a new barrier, they show a scattered distribution. These geographical barriers may arise due to the formation of mountains, formation of rivers or water bodies, elimination of land bridges, formation of islands, etc.

What are the Similarities Between Dispersal and Vicariance?

Dispersal and vicariance are two explanations for the disjunct distribution of organisms.
In both cases, organisms show geographically discontinuous distribution patterns.
Organisms separate due to a geographical barrier in both explanations.
They can lead to the differentiation of a new taxon due to allopatric speciation.
Furthermore, vicariance and dispersal are not mutually exclusive processes.

What is the Difference Between Dispersal and Vicariance?

Dispersal and vicariance are two theories that cause disjunct distribution of populations. In dispersal, part of the population migrates across an already existing geographical barrier into new region. In contrast, vicariance occurs due to appearance of a new geographical barrier that separates the population. Thus, this is the key difference between dispersal and vicariance.

Summary – Dispersal vs Vicariance

Dispersal and vicariance are two alternative biogeographic processes that explain disjunct distribution of organisms. Both processes cause the isolation of a population by a geographic barrier. In dispersal, the separation of a population occurs when a part of population migrates across a preexisting geographical barrier. In vicariance, the separation occurs due to the appearance of a new geographical barrier that divides the population. Thus, migration is responsible for dispersal while appearance of a new geographical barrier is responsible for vicariance. This is the summary of difference between dispersal and vicariance.

Reference:

1. Sanmartín, Isabel. “Historical Biogeography: Evolution in Time and Space.” SpringerLink, Springer US, 21 June 2012, Available here.
2. “Allopatric Speciation.” Wikipedia, Wikimedia Foundation, 18 Aug. 2019, Available here.