Multiple Dating Methods and Insights from the Fossil Record Reveal that Bark Beetles Predate the Angiosperm...

Estimating the age of a given clade is not trivial. Most dating studies rely on a node dating approach, which is highly sensitive to fossil placement uncertainties. A perfect example of that can be found in bark beetles (Curculionidae: Scolytinae). Molecular dating of the subfamily has often been anchored to a single fossil, †Cylindrobrotus pectinatus (~125 Ma), systematically used as a calibration point on the stem node of the subfamily. However, its phylogenetic position has never been tested through formal analyses, casting uncertainty over previous estimates. Here, we rely on total-evidence dating, integrating morphological and molecular data along with 19 scolytine fossils, to refine the divergence time estimates of the subfamily. We additionally used a traditional node-dating approach, and a fossil-only dating method, the Bayesian Brownian Bridge model, to estimate the age of the clade and compare the different results. Our findings suggest that †C. pectinatus is more closely related to Dryocoetini s.l. or Ipini-Dryocoetini s.l. clades rather than being a stem lineage of Scolytinae. In our case, when †C. pectinatus is inferred inside the subfamily, total-evidence dating with different pattern of branch rates across the tree (unlinking clocks for each gene and the morphological data), appeared more appropriate than node dating for estimating the age of Scolytinae, with ages ranging from ~149.9 to ~134.9 Ma. Under the same priors, node dating produced earlier ages, from ~195.4 to ~131.7 Ma, while the Bayesian Brownian Bridge produced ages ranging from ~168.4 to ~141.2 Ma. Across all methods, Scolytinae are constantly inferred to have diversified before the Angiosperm Terrestrial Revolution. These results highlight the importance of integrating multiple dating approaches to mitigate biases inherent to any single method, ultimately leading to more reliable divergence estimates.