UC San Diego

The role that environmental forcing plays in driving macroevolution is a fundamental question in paleontology. To rigorously test the effect of environmental change on biology, independent paleoecological and paleoenvironmental data are necessary. Cases where these types of quantitative data have been generated are rare; consequently few paleobiologic studies have the rigor to address such questions. The work presented here uses quantitative ecological data on Caribbean bivalve assemblages dating back to 11 Ma to address the question of cause and effect with regard to environmental change, ecologic change, and biologic interactions. Changes in the functional ecology of bivalve assemblages through time are linked to changes in Caribbean habitats. As coral reefs emerged as important habitats epifaunal bivalves became relatively more abundant constitutents of the bivalve assemblage. Likewise, as seagrass meadows became more common in the Caribbean, in conjunction with the emergence of coral reefs, bivalve diets diversified. Habitat also influenced biologic interactions. Predation intensity on bivalves increased in conjunction with the diversification of Caribbean habitats. Finally, throughout the Pliocene drilling among bivalve families remained constant, although drilling varies dramatically among bivalve taxa and is primarily related to life mode and habit. Thus, changes in the relative abundance of bivalves can also explain the observed differences in drilling intensity through time. As a whole, this research highlights the importance of environment in structuring communities and driving biological interactions. It also illustrates how the consequences of environmental perturbations may depend on cascades of ecological changes, with outcomes that are difficult to predict