Question

In a model by Wright (1940), the genetic differentiation among local populations was enhanced by metapopulation structure. In contrast, work by Slatkin (1987) suggested that metapopulation

structure can reduce genetic differentiation among populations. How can we reconcile thse two views? Explain how both can be true depending on the characteristics of the metapopulation?

Answer 1

In the model by Wright we see that when there is a phenomena of extintion/recolonization, there is a bigger set of smaller populations of the same species separated by space (that is the metapopulation structure). This separation makes genetic differentiation (which means how genetically different are the populations from each other) possible because they aquire mutations over time that makes each population different from each other. This can even separate them enough to evolve into two or more different species.

On the contrary, Slatkin states that when this phenomena exists, there is less possibility for genetic differentiation, but this only happens in specific circumstances: when there can be gene flow, that is for example, if the species is an animal and it can migrate to another local population of the same species, then there is an intercross of genes with procreation.

There is a third model, by Wade and McCaley (1988) that states in this particular case that there is a local population called the "Propagule pool" from which the individuals migrate, and there is another population, the "Migrant Pool" to which the individuals are atracted to migrate. The model of Wright comes true only in the Propagule Pool because there is no entrance of new genes and the population that stays starts to carry mutations that makes it different over time.