'Sum of inverse range-sizes' (SIR), a biodiversity metric with many names and interpretations

Abstract

Range restriction is an important measure of species rarity that is also interpreted as endemism. A simple biodiversity metric, the sum of inverse range-sizes, SIR, for species within a sampling unit is useful for conservation planning but has multiple names and applications, for example, to highlight areas of high biodiversity and biological uniqueness, the hotspots problem, e.g., weighted endemism, and as a range proportion-explicit metric for calculating complementarity in reserve selection, the representation problem, e.g., rarity-weighted richness, . This paper outlines the development, implementation and duplication of SIR. We propose that terminology for equivalent metrics can be unified if, -, SIR, refers to them generally, those based on site or grid cell occupancy, or area of occupancy, are referred to specifically as, range-rarity richness, while those aimed at measuring endemism based on extent of occurrence are referred to specifically as, georeferenced weighted endemism, . The phylogenetic equivalents would then be, phylogenetic range-rarity, and, georeferenced phylogenetic endemism, respectively.