The quality of the fossil record across higher taxa: compositional fidelity of phyla and classes in benthic marine associations

Although the fossil record preserves a wealth of historical data about past ecosystems, the current paradigm, which postulates that fossils provide faithful archives of ecological information, stems from research primarily focused on a single group of organisms known for their high fossilization potential: molluscs. Here, we quantify the fidelity of higher taxa (six phyla and 11 classes) by comparing live communities and sympatric dead remains (death assemblages) using comprehensive surveys of benthic marine invertebrates from coastal habitats in North Carolina (U.S.A). We found that although community composition differed between the two assemblages across phyla and classes, these differences were predictable with an overabundance of robust and more preservable groups. In addition, dead molluscs appear to be an excellent proxy for all taxa when tracking spatio-temporal patterns and shifts in community structure using a variety of ecological metrics, including measures of α, γ, and β diversity/evenness. This suggests that despite filters imposed by differential preservation of taxa and time-averaging, the fossil record is likely to be reliable with respect to relative comparisons of composition and diversity in shallow benthic marine paleocommunities. This is consistent with previous work indicating that shallow marine death assemblages can yield robust ecological estimates adequate for assessing the variability of ecosystems that existed under natural, pre-anthropogenic conditions.