The Relationship Between Global Diverisfication and Spatio-Temporal Transitions in Paleozoic Bivalvia

Over the past several years, a variety of macroevolutionary studies have focused on global diversification patterns exhibited by the earth's biota as a whole, as well as among constituent groups. One motivation for this increased attention is the recognition that analyses of temporal changes in global diversity can provide substantial insight into underlying macroevolutionary processes (e.g. Sepkoski, 1978, 1979, 1981, 1984; Sepkoski et al., 1981; Gould and Calloway, 1980; Carr and Kitchell, 1980; Kitchell and Carr, 1985; Miller and Sepkoski, 1988). Indeed, much about the dynamics of macroevolution has been elucidated through such investigations, but major diversity transitions in the history of life cannot be fully understood without consideration of the local, environmental/ecological contexts in which they took place. In other words, in the study of macroevolution, it is important to pay as much attention to the space dimension as has historically been paid to the time dimension. The utility of a spatio-temporal approach has been demonstrated in a series of studies conducted by Sepkoski and Sheehan (1983), Sepkoski and Miller (1985), Jablonski and Bottjer (1983), Bottjer and Jablonski (in press), Droser and Bottjer (1988), Bottjer et al. (1988), and Miller (1988, in press). Collectively, these investigations have suggested that major changes in the global diversities of several groups were accompanied by measurable paleoenvironmental shifts.