SEAFOOD THROUGH TIME REVISITED: THE PHANEROZOIC INCREASE IN MARINE TROPHIC RESOURCES AND ITS MACROEVOLUTIONARY CONSEQUENCES

Abundant paleobiological and geochemical evidence suggests that global marine nutrients and/or productivity increased over the Phanerozoic. Numerous previous studies have suggested that this increase, or episodes within it, have contributed to various significant patterns in the marine biota, including rise and fall of particular taxa; changes in “energetics” (biomass, metabolic rates, and physical activity such as predation); and taxonomic diversity. Yet the specific potential evolutionary mechanisms by which alterations in nutrients/productivity might cause such biotic changes have remained vaguely stated, contradictory, or obscure.

In order to pull together available information and focus attention on this issue, we have developed a new, synthetic curve of global average marine productivity for the Phanerozoic. We have then used simple but explicit models of the stages of allopatric speciation to develop a general theory (based in part on previous concepts of speciation on islands, such as Wilson's "Taxon Cycle" and the Grants’ “Speciation Cycle”) of how changes represented in this curve might have contributed to local, regional, and global taxonomic diversity patterns. The role of trophic resources (“food”) in species formation depends on where in the cycle of isolate formation, persistence, differentiation, and persistence/expansion a species is. The Speciation Cycle attempts to develop explicit and testable hypotheses of the frequently very different effects of food on each of these stages of speciation. Application of the Speciation Cycle to intervals of the Phanerozoic marine productivity curve may reveal and/or improve understanding of important connections between ecology and macroevolution.