Links between the species abundance distribution and the shape of the corresponding rank abundance curve

Species abundance distribution (SAD) is a classic topic of multispecies ecology. Different types of SAD may indicate specific environmental conditions. A possible way to present some properties of a theoretical or empirical SAD is the construction of a rank-abundance curve (RAC). With regard to the applicability of the RAC as a widely used indicator of the structure of a multispecies community and of the ecological status of its habitat, a basic question is the link between the type of SAD and the shape of the associated RAC. One of the simplest ways to characterize a RAC is to determine its concave and convex segments. However, none of ecological textbooks does give a clear-cut guideline concerning this issue. In the paper a connection is presented between some types of SAD and the convex and concave segments of the related RAC: including among others linearity for the geometric SAD (e.g. with communities in early stage of succession), convexity for the Zipf–Mandelbrot SAD (e.g. with communities with slow successional process), and convexity and then concavity with an inflexion point at approximately the mode of the associated histogram for the lognormal SAD (e.g. with climax, equilibrium communities). Our approach has the potential to improve and justify the use of RACs when searching for the determinants of community structure, initiating further studies in this field.

► Species abundance distributions (SAD) are used to characterize communities. ► Rank-abundance curves (RAC) are often used as indicators of SAD. ► However, the use of RAC to describe communities has no clear-cut justification. ► We demonstrate a connection between SAD and the concavity and convexity of the RAC. ► The shape of the RAC is linked with ecological processes underpinning communities.