Taxonomic flux as a measure of evolutionary turnover

Abstract

We introduce a new metric, "taxonomic flux", to quantify evolutionary trends both within and across taxonomic boundaries. This metric is normalized, which reduces the effect of sample size disparity between biologic groups and time intervals. Furthermore, this methodology considers stratigraphic range data as a whole, and measures relative growth or decline of diversity values as they deviate from system stability. Such trends may yield key information relating to evolutionary processes and forcing functions, especially if these trends are correlative within particular taxa or niche occupancy. Thus far, scientists and researchers have been stymied by absolute values derived from unequal datasets and by metrics designed only to quantify limited aspects of evolutionary dynamics. It is the purpose of this paper to demonstrate the utility of taxonomic flux both theoretically and from empirical study examining several invertebrate orders belonging to the classes Echinoidea, Bivalvia and Gastropoda. Taxonomic flux is an adaptable metric applicable to various levels of the taxonomic and ecological hierarchy thus enabling comparisons of the palaeontological record with that of the Recent.