Phanerozoic marine diversity: rock record modelling provides an independent test of large-scale trends

Abstract

Sampling bias created by a heterogeneous rock record can seriously distort estimates of marine diversity and makes a direct reading of the fossil record unreliable. Here we compare two independent estimates of Phanerozoic marine diversity that explicitly take account of variation in sampling-a subsampling approach that standardizes for differences in fossil collection intensity, and a rock area modelling approach that takes account of differences in rock availability. Using the fossil records of North America and Western Europe, we demonstrate that a modelling approach applied to the combined data produces results that are significantly correlated with those derived from subsampling. This concordance between independent approaches argues strongly for the reality of the large-scale trends in diversity we identify from both approaches.

Figure 1.

Comparative global marine biodiversity through time based on (a) raw counts of recorded taxa with range interpolation between first and last occurrences [27], and (b) sampled taxa recorded in the Paleobiology Database and corrected for variation in sampling using SQS (from [13]).

Figure 2.

(a) Plots of sampled genus richness versus rock area proxy for North America. (b) Same for Western Europe. (c) Residuals after subtracting North American rock record from Western Europe rock record showing comparative strengths of the two records. (d) Same for sampled diversity.

Figure 3.

(a) Plot of sampled genus richness for North America in the Paleobiology Database (black line) versus a model of what diversity would look like assuming true diversity is invariant and sampled diversity were driven solely by the rock area available in North America (grey line with 95% confidence intervals). (b) Residuals from subtracting the modelled diversity from the observed sampled diversity shown in (a). (c,d) Same for Western Europe. (e,f) Same for combined European and North American data. (g) Residuals from subtracting modelled diversity from the observed sampled diversity for Europe and North America combined (shaded area) plotted against SQS (from [13]), normalized around the mean (bars). (h) Correlation of modelled versus subsampled estimates of marine diversity.