Data and R code from: Global Phanerozoic biodiversity, can variation be explained by spatial sampling intensity

Variation in observed global generic richness over the Phanerozoic must be
partly explained by changes in the numbers of fossils and their geographic
spread over time. The influence of sampling intensity (i.e., the number of
samples) has been well addressed, but the extent to which the geographic
distribution of samples might influence recovered biodiversity is
comparatively unknown. To investigate this question, we create models of
genus richness through time by resampling the same occurrence dataset of
modern global biodiversity using spatially explicit sampling intensities
defined by the paleo-coordinates of fossil occurrences from successive
time intervals. Our steady-state null model explains about half of
observed change in uncorrected fossil diversity and a quarter of variation
in sampling-standardized diversity estimates. The inclusion in linear
models of two additional explanatory variables associated with the spatial
array of fossil data (absolute latitudinal range of occurrences, percent
of occurrences from shallow environments) and a Cenozoic step increase the
accuracy of steady-state models, accounting for 67% of variation in
sampling-standardized estimates and more than one third of the variation
in first differences. Our results make clear that the spatial distribution
of samples is at least as important as numerical sampling intensity in
determining the trajectory of recovered fossil biodiversity through time,
and caution the overinterpretation of both the variation and the trend
that emerges from analyses of global Phanerozoic diversity.