Taxonomic sufficiency in a live–dead agreement study in a tropical setting

Abstract

Community studies in paleontological research often rely on identification at taxonomic levels higher than species (mainly genus or family). Several studies have been conducted on paleo- and modern communities to identify the higher level of taxonomic identification that still depicts ecological patterns: genus- and, to a lesser extent, family-level identification are frequently sufficient. The use of higher taxonomic levels has not yet been explored in the context of studies comparing living and death assemblages (so-called “live–dead agreement studies”), notwithstanding their interest to quantify the fidelity of the fossil record and for environmental assessment. We conducted such exploration in a highly diverse tropical marine setting, targeting shelled molluscs. Our results suggest that the common practice of genus-level identification of paleontological samples allows for a proper reconstruction of the original biological community (e.g., variation in richness, ecological or taxonomic similarity) at the species level because (1) fidelity at the species and genus levels is very similar and (2) genera are sufficient to characterize between-habitat differences in composition and diversity. Live–dead agreement becomes even better at family and higher taxonomic levels for some metrics, but between-habitat differences in composition become weaker above the family level. However, at the genus and family levels, between-habitat differences are equally strong as at the species level. Genus-level identification may provide more robust results when one of the assemblages is dominated by a single species, because differences in abundance can be compensated by co-generic species. Moreover, in death and fossil assemblages, diagnostic characters get lost easily because of taphonomic processes such as abrasion, dissolution, and fragmentation; nonetheless, genus- and family-level identifications can still be reliable because the most conspicuous diagnostic characters which characterize higher taxa are more persistent after the death of the mollusc.