DOI: 10.5061/dryad.r7s92
title: Data from: Taxonomic and numerical sufficiency in depth- and salinity-controlled marine paleocommunities

description: Numerical and taxonomic resolution of compositional datasets affects
 investigator’s ability to detect and measure relationships between
 communities and environmental factors. We test whether varying numerical
 (untransformed, square-root- and fourth-root transformed relative
 abundance, and presence-absence data) and taxonomic resolutions (species,
 genera, families) reveal different insights into Lower to Middle Miocene
 molluscan communities along bathymetric and salinity gradients. The marine
 subtidal has a more even species-abundance distribution, a higher number
 of rare species, and a higher species-family and species-genus ratio than
 the three habitats with higher fluctuations in salinity and other physical
 parameters (marine and estuarine intertidal, estuarine subtidal).
 Taxonomic aggregation and numerical transformation of data result in very
 different ordinations, although all habitats differ significantly from
 each other at all taxonomic and numerical levels. Rank correlations
 between species-level and higher-taxon, among-sample dissimilarities are
 very high for proportional abundances and decrease strongly with
 increasing numerical transformation, most notably in the two intertidal
 habitats. The proportion of variation explained by depth is highest for
 family-level data, decreases gradually with numerical transformation, and
 is higher in marine than in estuarine habitats. The proportion of
 variation explained by salinity is highest for species-level data,
 increases gradually with numerical transformation, and is higher in
 subtidal than in intertidal habitats. Therefore, there is no single best
 numerical and taxonomic resolution for the discrimination of communities
 along environmental gradients: the “best” resolution depends on the
 environmental factor considered and the nature of community response to
 it. Different numerical and taxonomic transformations capture unique
 aspects of metacommunity assembly along environmental gradients that are
 not detectable at a single level of resolution. We suggest that
 simultaneous analyses of community gradients at multiple taxonomic and
 numerical resolutions provide novel insights into processes responsible
 for spatial and temporal community stability.
description: Supplementary figure
 1Rank
 abundance distributions for habitats at three taxonomic
 levelsSuppl_fig_1.pdfSupplementary figure 2Evenness and species richness of the four habitats at three taxonomic levels.Suppl_fig_2.pdfSupplementary figure 3Distribution of p-values from Mantel test for Spearman correlation between dissimilarity matrices representing different taxonomic and numerical levels. A-C, Correlation between taxonomic levels at different numerical resolutions. D-F, Correlation between proportional abundance data and higher levels of numerical transformation. Filled points represent median p-values across 1000 subsampling iterations, empty points are outliers that lie beyond 1.5 times the interquartile range from the upper quartile.Suppl_fig_3.pdfSupplementary figure 4NMDS ordination of a double-standardized subsample of the total dataset comparing individual habitats along the depth- and salinity gradient for species and families using proportional abundances and presence/absence data. Environmental assignment of samples: estuarine intertidal – black points, estuarine subtidal – red squares, marine intertidal – green diamonds, marine subtidal – blue triangles.Suppl_fig_4.pdfSupplementary figure 5Effect of taxonomic aggregation and numerical transformation on NMDS ordination patterns in the total non-standardized dataset. Results for square-root and fourth-root transformed proportions were omitted for clarity and showed patterns intermediate between proportional and presence/absence data. Environmental assignment of samples: estuarine intertidal – black points, estuarine subtidal – red squares, marine intertidal – green diamonds, marine subtidal – blue triangles.Suppl_fig_5.pdfSupplementary figure 6Distribution of p-values from PERMANOVA comparing molluscan assemblages along the depth- and salinity gradients at different levels of taxonomic aggregation and numerical resolution. A, In the total dataset (all four habitats considered) B, Along environmental gradients (pairwise comparisons of habitats). Filled points represent median P-values across 1000 subsampling iterations, thick lines denote interquartile range (IQR), whiskers (thin lines) encompass data points scattered less than 1.5 times the IQR from the lower and upper quartile and outliers are marked as empty points.Suppl_fig_6.pdf