DOI: 10.5061/dryad.313dq
title: Data from: On the benefits of being redundant: low compositional fidelity of diatom death assemblages does not hamper the preservation of environmental gradients in shallow lakes

description: Comparisons between death assemblages and their source living communities
 are among the most common actualistic methods of evaluating the
 preservation of compositional and environmental information in fossil
 assemblages. Although live-dead studies have commonly focused on marine
 mollusks, the potential of diatoms to preserve ecological information in
 continental settings has been overlooked. Thus, little is known about the
 nature and magnitude of the taphonomic biases affecting live-dead
 agreement of diatom assemblages, despite their extensive application as
 modern 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 environmental fidelity exhibited
 by diatom death assemblages in shallow lakes. I find that diatom death
 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 time-averaged DAs and non-averaged LAs,
 and (2) differential preservation of diatom taxa related to the intrinsic
 properties of their valves. Despite compositional dissimilarities, DAs
 were able to capture the same environmental gradients as LAs, with high
 significance. This decoupling between live-dead agreement in community
 composition and community response to gradients can be related to the
 existence of at least two mutually exclusive subsets of species that
 significantly captured compositional dissimilarities based on the full set
 of the species in the three lakes. This functional redundancy implies that
 the between-sample relationships of living assemblages can be
 significantly preserved by DAs even if some taxa are removed by taphonomic
 processes. The preservation of environmental gradients thus does not
 require good preservation of all living taxa. Structural redundancy
 compensates for the loss of compositional fidelity caused by postmortem
 processes in the diatom data set.
description: Supplementary Table
 1Monte Carlo calculation
 mean differences on richness (S), Simpson (1-D) and Shannon (H’) diversity
 indices and associated p-values comparing LAs (living assemblages) and DAs
 (dead assemblages) and open water and littoral environments from Las
 Mostazas (LM), Los Carpinchos (LC) and Nahuel Rucá (NR). Significant
 values at α = 0.05 are in boldface.Supplementary Table
 2List
 of diatom species mentioned in the text, their authorities and life form,
 salinity and nutrient classifications (according to de Wolf, 1982; Denys,
 1991/1992 and Van Dam, 1994). E: epiphyte; B: benthic; Aer: aerophilous;
 P: plankton; Tp: tychoplankton; H: halophobous; OI: oligohalobous
 indifferent; OH: oligohalobous halophilous; M: mesohalobous; PO:
 polyhalobous; Dys: dystrophic; Eu: eutrophic; Mt: mesotrophic; Ot:
 oligotrophic; I: indifferent.Supplementary Table
 3Results of HMD
 (Homogeneity in Multivariate Dispersions) tests comparing live and dead
 diatom assemblages in total (littoral+open waters), littoral and open
 waters datasets showing: ratio (premortem variation/total LD variation),
 the estimates of premortem and postmortem variation, the significance
 values of modified test of multivariate dispersions, which indicates
 whether variation among DAs and the centroid of LAs is larger
 (overdispersion) or smaller (underdispersion) than variation among LAs and
 their centroid. NS= not significant at α = 0.05.Supplementary Table
 4Results of HMD
 ((Homogeneity in Multivariate Dispersions) tests comparing littoral and
 open waters dispersions. Significant values at α = 0.05 are in
 boldfaceSupplementary Table
 5Gradient lengths and
 results of CCA ordinations of live and death diatom assemblages against
 vegetation cover (veg) and depth in the three studied lakes. Significant
 ordinations at α = 0.05 are in boldface.Supplementary Table
 6Gradient lengths and
 results of CCA ordinations of live and death diatom assemblages against
 conductivity, pH, Secchi depth and depth in the three-lake combined
 dataset. Significant ordinations at α = 0.05 are in
 boldface.Supplementary Table
 7Percentage variance
 explained by each environmental variable in LAs and DAs as calculated by
 partial CCA. The significance is indicated based on 199 unrestricted ANOVA
 like permutations (p &lt; 0.05*, p &lt; 0.01**, p &lt;
 0.001***).