Dynamic aspects of diversity

Abstract

Abstract. Ecological diversity is viewed as a measure of information, as the variety of messages compounded with the number of individuals belonging to different species. Two limit situations of diversity are indicated: a chemostat‐like system tending to become monospecific, and a Noah's ark or museum situation with an infinite number of species each represented by just one specimen. In a dynamic approach, two differential equations for S, the number of species, and N, the number of individuals, can be considered. A new index of diversity is proposed based on these two equations.The concept of diversity spectrum is proposed for a series of diversity measurements in samples of increasing size and related to the concept of minimal area. Diversity can also be measured on non‐taxonomic categories, e.g. size classes.The contrast between the two boundary types, limes convergens (ecotone) and limes divergens (ecocline), is emphasized. The nature of the difference between them is compared with that of tension zones between fluids in contact.Differences between ecosystems can be characterized through differences in the ratio P/B (Production/Biomass) and a boundary situation is imagined including two systems with P/B different values and different diversity levels. Some examples are presented from communities in streams.