Apparent timescaling of fossil diversification rates is caused by sampling bias

Abstract

Negative scaling relationships between both speciation and extinction rates on the one hand, and the age or duration of organismal groups on the other, are pervasive and recovered in both molecular phylogenetic and fossil time series. The consistency between molecular and fossil data hints at a universal cause, and potentially to incongruence between micro- and macroevolution. However, the existence of negative rate scaling in fossil time series has not undergone the same level of scrutiny as in molecular data. Here, we analyse the marine fossil record across the last ~535 Ma of the Phanerozoic to investigate the presence and strength of negative rate scaling. We find that negative rate scaling arises under commonly applied age range-based per-capita rates, which do not control for sampling bias, but are severely reduced or absent when metrics are used that do correct for sampling. We further show by simulation that even moderate incomplete sampling of species occurrences through time may induce rate scaling. We thus conclude that there are no significant scaling relationships present in these fossil clades, and that any apparent trend is caused by taxonomic practices and sampling artefacts. If rate scaling appears genuinely in molecular phylogenies, the absence of such a relationship in the fossil record will provide a valuable benchmark and constraint on what processes can cause it.