Public Library of Science, PLoS ONE, 9(16), p. e0256679, 2021
DOI: 10.1371/journal.pone.0256679
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Molecular clocks have become powerful tools given increasing sequencing and fossil resources. However, calibration analyses outcomes depend on the choice of priors. Here, we revisited the seminal dating study published by Andújar and coworkers of the genusCarabusproposing that prior choices need re-evaluation. We hypothesized that reflecting fossil evidence and the Gondwanan split properly significantly rewinds the molecular clock. We re-used the dataset including five mitochondrial and four nuclear DNA fragments with a total length of 7888 nt. Fossil evidence for Oligocene occurrence ofCalosomawas considered. Root age was set based on the fossil evidence of Harpalinae ground beetles in the Upper Cretaceous. Paleogene divergence of the outgroup taxa Ceroglossini and Pamborini is introduced as a new prior based on current paleontological and geological literature. The ultrametric time-calibrated tree of the extended nd5 dataset resulted in a median TMRCACarabusof 53.92 Ma (HPD 95% 45.01–63.18 Ma), roughly 30 Ma older than in the Andújar study. The splits amongC.rugosusandC.morbillosus(A),C.riffensisfrom the EuropeanMesocarabus(B), andEurycarabusandNesaeocarabus(C) were dated to 17.58 (12.87–22.85), 24.14 (18.02–30.58), and 21.6 (16.44–27.43) Ma. They were decidedly older than those previously reported (7.48, 10.93, and 9.51 Ma). These changes were driven almost entirely by constraining the Carabidae time-tree root with a Harpalinae amber fossil at ~99 Ma. Utilizing the nd5 dating results of three well-supportedCarabusclades as secondary calibration points for the complete MIT-NUC dataset led to a TMRCA ofCarabusof 44.72 (37.54–52.22) Ma, compared with 25.16 Ma (18.41–33.04 Ma) in the previous study. Considering fossil evidence for OligoceneCalosomaand Late Cretaceous Harpalini together with the Gondwanan split as a new prior, our new approach supports the origin of genusCarabusin the Eocene. Our results are preliminary because of the heavy reliance on the nd5 gene, and thus will have to be tested with a sufficient set of nuclear markers. Additionally, uncertainties due to dating root age of the tree based on a single fossil and outgroup taxon affect the results. Improvement of the fossil database, particularly in the supertribe Carabitae, is needed to reduce these uncertainties in datingCarabusphylogeny.