Beta diversity

Beta diversity is a measure of the ecological diversity (engl: diversity, Germanized to diversity) at a medium spatial plane, the so-called landscape level. The term is defined in a theory of the American ecologist Robert H. Whittaker ( Whittaker 1960) and is used only in the context of the application of his theory. Measure of ecological diversity is here primarily the respective number of species.

Definition and measurement

Whittaker first consider the local variety at a certain point ( a part of Habitat, a specimen surface, etc.), which he called alpha diversity. At a higher level, the increase in diversity then depends mainly on how different the various individual points with each other. This is also "between habitat" or "species turnover" ( mode change ) called. The fewer types have in common the habitats ( for a given alpha - diversity), the greater is the beta diversity. Are all local communities to all local points identical, beta diversity is minimal. Do not they have a single species in common, it is maximum. The beta diversity is particularly relevant when considering the impact of variations in living conditions (such as temperature or moisture gradients as Habitatgradienten ).

The introduction of beta diversity as a measure intended to mainly serve to distinguish between local and regional effects. Thus, a community locally consist of very many kinds, so have high alpha diversity, be regional but uniform, so that the same species-rich community in the same composition occurs everywhere. In contrast, the community of all examined species-poor locations rather be (low alpha diversity ), but regionally very different. So high alpha and high beta diversity must not be related to each other.

To determine the beta diversity, one can determine the ratio between the total number of species in all individual measurements to the mean number of species of these measurements. Specific assumptions on the distribution pattern is not necessary.

Plotting the individual measurements, sorted by number of their species, the species- poorest to the richest, in a diagram in which one is not the absolute number of species each measurement, but only the species adds that have been added by a new measurement / a new partial habitat ( a so-called species -rank chart ), the beta diversity shows in the slope of the resulting curve. The curve strives asymptotically to a saturation level when removed by adding additional samples the number of species no longer rises, ie the regional species pool is fully covered. In other cases, the measured value for the beta diversity nor the acquisition effort depends and should be interpreted with caution.