title: An evaluation of fossil tip-dating versus node-age calibrations in tetraodontiform fishes (Teleostei: Percomorphaceae).
abstract: Time-calibrated phylogenies based on molecular data provide a framework for comparative studies. Calibration methods to combine fossil information with molecular phylogenies are, however, under active development, often generating disagreement about the best way to incorporate paleontological data into these analyses. This study provides an empirical comparison of the most widely used approach based on node-dating priors for relaxed clocks implemented in the programs BEAST and MrBayes, with two recently proposed improvements: one using a new fossilized birth-death process model for node dating (implemented in the program DPPDiv), and the other using a total-evidence or tip-dating method (implemented in MrBayes and BEAST). These methods are applied herein to tetraodontiform fishes, a diverse group of living and extinct taxa that features one of the most extensive fossil records among teleosts. Previous estimates of time-calibrated phylogenies of tetraodontiforms using node-dating methods reported disparate estimates for their age of origin, ranging from the late Jurassic to the early Paleocene (ca. 150-59Ma). We analyzed a comprehensive dataset with 16 loci and 210 morphological characters, including 131 taxa (95 extant and 36 fossil species) representing all families of fossil and extant tetraodontiforms, under different molecular clock calibration approaches. Results from node-dating methods produced consistently younger ages than the tip-dating approaches. The older ages inferred by tip dating imply an unlikely early-late Jurassic (ca. 185-119Ma) origin for this order and the existence of extended ghost lineages in their fossil record. Node-based methods, by contrast, produce time estimates that are more consistent with the stratigraphic record, suggesting a late Cretaceous (ca. 86-96Ma) origin. We show that the precision of clade age estimates using tip dating increases with the number of fossils analyzed and with the proximity of fossil taxa to the node under assessment. This study suggests that current implementations of tip dating may overestimate ages of divergence in calibrated phylogenies. It also provides a comprehensive phylogenetic framework for tetraodontiform systematics and future comparative studies.
authors.affiliation: Department of Biological Sciences, The George Washington University, 2023 G St. NW, Washington, DC 20052, United States; Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, P.O. Box 37012, MRC 159, Washington, DC 20013, United States. Electronic address: arciladk@gmail.com.
authors.forename: Dahiana
authors.initials: D
authors.lastname: Arcila
authors.affiliation: Department of Biological Sciences, The George Washington University, 2023 G St. NW, Washington, DC 20052, United States.
authors.forename: R
authors.initials: R
authors.lastname: Alexander Pyron
authors.affiliation: Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, P.O. Box 37012, MRC 159, Washington, DC 20013, United States.
authors.forename: James C
authors.initials: JC
authors.lastname: Tyler
authors.affiliation: Department of Biological Sciences, The George Washington University, 2023 G St. NW, Washington, DC 20052, United States.
authors.forename: Guillermo
authors.initials: G
authors.lastname: Ortí
authors.affiliation: Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, P.O. Box 37012, MRC 159, Washington, DC 20013, United States; Department of Biology, University of Puerto Rico - Río Piedras, P.O. Box 23360, San Juan 00931, Puerto Rico.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Betancur-R
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D005075:Biological Evolution; D002138:Calibration; D002965:Classification / Q000379:methods*; D005580:Fossils; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D023721:Tetraodontiformes / Q000145:classification*
keywords: Acanthomorph diversification; Fossil record; Molecular clock calibration; Tetraodontiformes; Tip-dating method