15 Evidence of the evolution of species - Part IX: dispersion different from wild birds

Gene flow caused by migration, for example, can destroy the adaptation to local conditions, opposed to evolutionary differences in the populations, but also between them. Indeed, classical theory of population genetics suggest that the local populations and migrating împerecheaz? more between them, so there are more genetic similarities. This concept seems to be consistent with common sense and assumes that genes fluctuation is a chance such as diffusion. But neîntâmpl?toare dispersal may promote local adaptation and evolutionary differentiation as Ben Sheldon and his colleagues from the Institute of ornithology Edward Gray of Oxford, UK, announced in 2005. 

Their work was part of a study conducted several decades on birds, Parus major, living in a forest in Oxfordshire, UK. Researchers have discovered that the type and quantity of genetic variation in weight of these chicks songster differ from one part to another forest. This pattern of variation leads to different responses of selection in distinct parts of the forest, leading to local adaptation. 

The effect is strengthened by the dispersion neîntâmpl?toare; birds choose împerecheaz? and in different habitats in a way that increases their physical condition. The authors then concluded that "when gene flow is not homogeneous, evolutionary differentiation can be rapid and may occur on territories surprisingly small. 

In another study involving these birds, made the island Vlieland, Holland, and published the same issue of Nature, Erik Postma and Arie van Noordwijk of the Netherlands Institute of Ecology in Heteren found that gene flow, mediated dispersal fixed , maintains a large genetic difference in the size of eggs in a small space, illustrating, again, what scientists call "the great effect of migration in the evolution of local adaptation and population genetic structure.