Molecular dating of the teleost whole genome duplication (3R) is compatible with the expectations of delayed rediploidization.

Vertebrate evolution has been punctuated by three whole genome duplication (WGD) events that have been implicated causally in phenotypic evolution, from the origin of phenotypic novelties to explosive diversification. Arguably the most dramatic of these is the 3R WGD event associated with the origin of teleost fishes which comprise more than half of all living vertebrate species. However, tests of a causal relationship between WGD and teleost diversification have proven difficult due to the challenge of establishing the timing of these phenomena. Here we show, based on molecular clock dating of concatenated gene alignments, that the 3R WGD event occurred in the early-middle Permian (286.18-267.20 Million years ago; Ma), 52.02-12.84 million years (Myr) before the divergence of crown-teleosts in the latest-Permian-earliest Late Triassic (254.36-234.16 Ma) and long before the major pulses of teleost diversification in Ostariophysi and Percomorpha (56.37-100.17 Myr and at least 139.24-183.29 Myr later, respectively). The extent of this temporal gap between putative cause and effect precludes 3R as a deterministic driver of teleost diversification. However, these age constraints remain compatible with the expectations of a prolonged rediploidization process following WGD which, through the effects of chromosome rearrangement and gene loss, remains a viable mechanism to explain the evolution of teleost novelties and diversification.