LIVE-DEAD COMPARISONS OF THE MARINE BENTHOS SUGGEST THAT FOSSIL ASSEMBLAGES ARCHIVE TROPHIC INFORMATION WITH HIGH FIDELITY

Determining the extent to which the fossil record can provide faithful archives of past ecological conditions is increasingly important for conservation and ecosystem management. Although functional composition can be used to understand organic-matter processing and ecosystem functioning, quantitative assessments of the preservation of relative proportions of organisms from various trophic groups in paleontological data, or trophic fidelity, are rare. Herbivores and suspension feeders may be overrepresented in death assemblages, and differences in abundance and life-span across groups may lead to differences in the fidelity of trophic structure.

Here, we quantify the reliability of paleontological data across multiple phyla in macro-benthic invertebrate communities of coastal North Carolina (U.S.A) using live-dead comparisons of assemblage-level samples. We evaluate three critical components of ecological fidelity: composition, diversity, and trophic structure. In absolute numerical terms, preservable taxa may be a poor proxy for estimating diversity and abundance of all organisms that were originally present in the entire community and geohistorical assemblages do not faithfully record the relative abundance of all higher taxa. However, locality-level live-dead fidelity was high, and richness and abundance estimates were strongly correlated. Our results show that compositional and diversity fidelity varies predictably across taxonomic groups, and that molluscs characterize relative spatio-temporal patterns representative of the entire community. Despite differences in composition, trophic fidelity was very high, and nearly all trophic groups were represented in similar proportions in death assemblages and the fossil record, indicating that trophic composition is an excellent candidate for conservation paleobiology and paleoecology.

These results suggest that preservable taxa may be an excellent proxy for all taxa when tracking shifts in community composition, diversity, or trophic structure. This is a promising outcome considering that conservation and paleoecology focus largely on relative changes. Highly preservable taxa can be a meaningful proxy in quantitative studies examining local spatial and temporal trends in biodiversity and composition.