FALLACIES OF THE DISHARMONIOUS INDEX AND RELEVANCE OF QUATERNARY NON-ANALOGUE MAMMAL FAUNAS FOR FUTURE GLOBAL ENVIRONMENT CHANGE

Frequent and repeated climate fluctuations of the late Quaternary serve as a “natural experiment” for species response to environmental change. Analysis of the FAUNMAP database documents individualistic shifts in the geographic distributions for late Quaternary mammals. Because these shifts are not necessarily random and because many species share similar niche parameters, some species appear to form coherent groups of core species but their response is still individualistic. This response has created Quaternary biotic communities without modern analogues which has profound implications for the design of biological reserves and for land use management with respect to future global climate change. The relevance of non-analogue mammal communities has been challenged by Alroy who claims that non-analogue associations were not common in the Quaternary and that they appeared to occur in both the Pleistocene and Holocene. Re-examination of his analysis of the Disharmonious Index shows that he employed a non-traditional definition for non-analogue faunas and that his methods created artificially low counts and consequently an underestimate of their significance. New quantitative analyses with the traditional definition document their relatively high abundance in the Pleistocene, low frequency in the Holocene and wide geographic distribution in North America.