On the benefits of being redundant: Low compositional fidelity of diatom death assemblages does not hamper the preservation of environmental gradients in shallow lakes

BERNAVA GUSTAVO VICENTE; HASSAN GABRIELA

PALEOBIOLOGY

PALEONTOLOGICAL SOC INC

Lugar: Lawrence; Año: 2015

0094-8373

Abstract.—Comparisons between death assemblages and their source living communities are among themost common actualistic methods of evaluating the preservation of compositional and environmentalinformation in fossil assemblages. Although live-dead studies have commonly focused onmarine mollusks, the potential of diatoms to preserve ecological information in continental settings hasbeen overlooked. Thus, little is known about the nature and magnitude of the taphonomic EN ESTE ARTICULO SE ME AGRADECE LA COLABORACIONbiases affecting live-dead agreement of diatom assemblages, despite their extensive application asmodern and fossil bioindicators in paleoecological and paleoenvironmental reconstructions.In this study, I analyzed three live-dead data sets in order to evaluate the compositional and environmentalfidelity exhibited by diatom death assemblages in shallow lakes. I find that diatomdeath assemblages (DAs) do differ significantly in their taxonomic composition from living assemblages(LAs), mainly as a consequence of (1) differences in the temporal resolution between timeaveragedDAs and non-averaged LAs, and (2) differential preservation of diatom taxa related to theintrinsic properties of their valves. Despite compositional dissimilarities, DAs were able to capturethe same environmental gradients as LAs, with high significance. This decoupling between live-deadagreement in community composition and community response to gradients can be relatedto the existence of at least two mutually exclusive subsets of species that significantly captured compositionaldissimilarities based on the full set of the species in the three lakes. This functional redundancyimplies that the between-sample relationships of living assemblages can be significantlypreserved by DAs even if some taxa are removed by taphonomic processes. The preservation ofenvironmental gradients thus does not require good preservation of all living taxa. Structuralredundancy compe