The productivity and biodiversity of an ecosystem is significantly affected by the rate at which organisms move between different parts of the ecosystem. When there is little or no dispersal, populations of species that remain in harsh areas of an ecosystem are unable to adapt to their environment due to a low population size and lack of genetic variation. Conversely, when there is too much dispersal in an ecosystem, species evolve to be 'generalists' that can survive in many habitats, but fail to thrive in any given one. The scientific team behind this new research found that both the biodiversity and productivity of an ecosystem are at a peak when there is an intermediate rate of dispersal of species - not too little and not too much - between different parts of the ecosystem.
Source: ScienceDaily