VII.2.5 Gene flow limits the population’s ability to adapt optimally to local conditions.

While the impact of gene flow is clearly positive in that it helps to maintain genetic polymorphism and thus also the ability of the local population to optimally respond to changes in the environment, from the perspective of the population’s ability to adapt optimally to long-term stable conditions in a given environment, its impact is rather negative. Microevolutionary adaptation of the population to local conditions is achieved by fine-tuning the frequency of the alleles in the population’s gene pool. The frequency of the alleles introduced into local population’s gene pool by migrants equals that of the surrounding populations, which constantly tips the composition of the local population’s gene pool off its optimal value. 

            It has been observed, for example, that a relatively isolated blue tit population living in the evergreen forests of Corsica nests later than the tit population on the continent, a beneficial behaviour in that particular environment because it ensures that the time of feeding the offspring coincides with the peak insect levels in the evergreen forests. On the other hand, a minority tit population living in the evergreen forests on the continent nests earlier, simultaneously with the tit populations living in the surrounding dominant deciduous forests, which makes the timing of feeding its offspring inconvenient in relation to insect rates in the relevant locations. It is assumed that gene flow from the surrounding populations prevents the populations on the continent from adapting optimally to the conditions of their local environment (Dias & Blondel 1996).

Was this information useful for you?
The classical Darwinian theory of evolution can explain the evolution of adaptive traits only in asexual organisms. The frozen plasticity theory is much more general: It can also explain the origin and evolution of adaptive traits in both asexual and sexual organisms Read more
Draft translation from: Evoluční biologie, 2. vydání (Evolutionary biology, 2nd edition), J. Flegr, Academia Prague 2009. The translation was not done by biologist, therefore any suggestion concerning proper scientific terminology and language usage are highly welcomed. You can send your comments to flegratcesnet [dot] cz. Thank you.