Spatial and temporal patterns of species diversity in montane mammal communities of western North America

We present the results of the first analysis of distributional patterns of the same taxa across thousands of kilometres and thousands of years, which demonstrate that the exponents for the power relationships in space and tim e are similar. In both space and time, the distribution of mammalian taxa o f the Great Basin and Rocky Mountains follows a 'nested subset' pattern. We conclude that species identities and their relative abundances are non-ran dom properties of communities that persist over long periods of ecological time and across geographic space. This is consistent with species abundance contributing heavily to evolutionary patterns, and allows predictions of h ow species within communities will respond to future global change.