Every border has different characteristics in respect of the central parts of a distribution. The defensive role or the offensive role of border behavior is a general rule for individual entities as well as for populations and communities. According to this universal paradigm, we can describe ecotone properties according to the different entity considered.
Moving from individual to community, ecotonal properties have in common the variance in the explicit phenomena.
Under the different environmental conditions in a population, the allelic frequency of a gene can change creating a genotone (Dobzhansky et al. 1977). An individual intercepts a discontinuity changing the behavior. A population close to an ecotone can change the density of individuals, and a community the composition of species.
A population can increase or decrease the density according to the presence of a less favorable (decrease in local density) or more favorable (increase in local density) habitat (Fig. 6.5). A community can have a richer or poorer composition at the border accordingly.
Fig. 6.5 Change in local density of a population at an ecotone. In A the border represents a more hostile field and the population shows a rarefaction. In B the border is an attractive place and individuals are more concentrated around it
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