摘要

Measuring species diversity is critical for ecological research and biodiversity conservation. The separate assessment of within-unit diversity and unit distinctiveness in the form of endemism may Lead to biased results when evaluating the importance of a unit for regional diversity. In this paper, we adopt the additive partitioning of species diversity and propose a series of measurements decomposing the contribution of a unit into two components, one based on within-unit species diversity and the other on unit distinctiveness, for species richness and Simpson's index. We also propose a differentiation coefficient to evaluate the distribution of species diversity within and among units and to compare the relative importance of unit distinctiveness and within-unit diversity for regional diversity. Using simulations and a real data set of tree species in a community consisting of nine plots, we compared the proposed method with other ranking methods. The definition of unit-specific additive components of species diversity facilitates diversity scaling in hierarchical systems. The individual components may be used to identify the factors determining the contribution of a unit to larger-scale diversity, while avoiding typical problems associated with the number of endemic species. The ranking of units based on an integrated assessment of alpha and beta diversity at the unit level provides an objective foundation for determining conservation priorities.