Rényi's generalized information as a linear combination of species richness and dominance concentration

Intuitively, biological diversity would apparently seem the most unambiguous and easily studied of ecological concepts. However, when we look for a suitable numerical definition, we find that no single diversity index adequately summarizes community structure. One reason for this drawback is that different diversity indices confound the qualities of species richness and dominance concentration in a single number. Consequently, the characterization of community diversity can be substantially improved by substituting a parametric index family for traditional diversity indices, While traditional diversity indices supply point descriptions of community structure, according to parametric diversity indices, there is a continuum of possible diversity measures, which differ only in their sensitivity to the presence of rare species in the formulation of the indices. In this paper we first summarize the role of Renyi's generalized information for parametric biodiversity characterization. Then, we show that Renyi's generalized information can be expressed as a simple linear combination of the information associated to species richness and dominance concentration. Raunkiaer's life-form spectra of a Mediterranean garrigue in southern France one year and five years after fire are used to clarify the ideas discussed.