CRETACEOUS CARIBBEAN REEFS, HIERARCHY THEORY AND PUBLIC POLICY

The oldest occurrences of rudist bivalves in the Caribbean and circum-Caribbean region are in Lower Cretaceous Berriasian-Valanginian rocks in Venezuela and Texas. Rudists were not major components of Caribbean ecosystems until the mid-Cretaceous, when a change in taxonomic composition from coral-algal to rudist-dominated ecosystems occurred. An analysis of rudist bivalve species diversity per stage reveals that speciation was lowest in the Barremian with 2 species/My over a period of 6 My, and highest in the Maastrichtian with 19.4 species/My over a 6 My period. Lower and mid-Cretaceous rudists were associated with carbonate substrates, but Upper Cretaceous localities show carbonate, volcaniclastic and siliciclastic sediments associated with frameworks. Paleobiologic and environmental processes contributed to the development of reefs and to the latitudinal shifts in species diversity from 20-30 degrees N paleolatitude in the mid-Cretaceous to 10-20 degrees N in the Late Cretaceous.

In Cretaceous reefs, scleractinian corals and rudist bivalves identify the reproductive process or the flow of genetic information in the reef ecosystem, for species are components of only the genealogical hierarchy. Trophic groups and guild structures provide data for testing the persistence of matter-energy transfer and the ecological hierarchy in Cretaceous reefs. Results indicate that both regional and the Cenomanian-Turonian extinctions interrupted the flow of species, for new genera and the dominance of different families are apparent after extinction boundaries. However, the ecological hierarchy was not affected by these same extinctions. The terminal Cretaceous mass extinction was the only event that interrupted both genealogical flow and matter-energy transfer, as evidenced by the extinction of rudists and the global disappearance of the reef ecosystem for 7-10 My.

If data from the Cretaceous rock record were used to evaluate modern evolutionary processes on reef ecosystems, we might surmise that the preservation of trophic groups and guild structures would be more valuable than the preservation of a single species if the health of our reefs were endangered. However, focus is placed only on the genealogical record in modern policy design theory.