- The Paleontological Society
DOES THE HISTORY OF GLOBAL DIVERSITY MATTER?
Regardless of the macroevolutionary issues at stake, most students of biodiversity would agree that there is value in calibrating global biodiversity trends through critical intervals. To cite one obvious example, given the overwhelming interest in mass extinctions, we would certainly like to know the extent to which diversity declined during these events. Just as significantly, if we are to argue that any mass extinction was truly a global phenomenon, we must demonstrate definitively that its biotic effects reached around the world. Clearly, “standard” global compendia (e.g., Sepkoski 1992, 2002) are insufficient for the latter objective, because they contain no geographic or environmental information. At the least, a database that compares biodiversity transitions among different regions or paleoenvironments is required. Such analyses have the added benefit of providing opportunities to evaluate geographic and environmental selectivity in extinctions, an important facet of any attempt to understand what caused them (e.g., Raup and Jablonski 1993; Jablonski and Raup 1995).
However, beyond the desire to assess mass extinctions and other globally mediated biotic events, does an accurate read of global diversity through a given stratigraphic interval really tell us anything that we could not learn about macroevolutionary processes simply by focusing on one or a few well-studied regions? After several decades of intense investigation, this question remains contentious. Even among the four authors who reached a landmark consensus about the trajectory of Phanerozoic global diversity (Sepkoski et al. 1981), there was no consensus about what produced the pattern. On the one hand, Bambach (1977) suggested that Phanerozoic trends in median species richness within communities (a proxy for alpha diversity [see Sepkoski 1988]) paralleled trends exhibited in aggregate, global compilations of taxonomic richness. Further, in evaluating the ecological propensities of Sepkoski's (1981) three evolutionary faunas, Bambach (1985) argued that increases in the …