An index of divergence from species to life-form diversity based on the notion of intrinsic diversity ordering

In this paper, we propose a measure of divergence from species to life-form diversity based on the notion of intrinsic diversity ordering. First, species and life-form relative abundances within the analyzed community are determined. Next, community intrinsic diversity profile is computed both from species and life-form relative abundances. Finally, the speed of decrease from species to life-form diversity is obtained by comparing the area under the species diversity profile with the area under the corresponding life-form diversity profile. Since life-forms classify plants into ecologically relevant groups irrespective of their systematics, the proposed measure might be useful to quantify the ecological similarity of different communities without loosing information on traditional taxonomic diversity figures. As an application for demonstration, a small data set from a garigue community on ultramafic soils of Tuscany (central Italy) is used.