title: Phylogenetic relationships and timing of diversification in gonorynchiform fishes inferred using nuclear gene DNA sequences (Teleostei: Ostariophysi).
abstract: The Gonorynchiformes are the sister lineage of the species-rich Otophysi and provide important insights into the diversification of ostariophysan fishes. Phylogenies of gonorynchiforms inferred using morphological characters and mtDNA gene sequences provide differing resolutions with regard to the sister lineage of all other gonorynchiforms (Chanos vs. Gonorynchus) and support for monophyly of the two miniaturized lineages Cromeria and Grasseichthys. In this study the phylogeny and divergence times of gonorynchiforms are investigated with DNA sequences sampled from nine nuclear genes and a published morphological character matrix. Bayesian phylogenetic analyses reveal substantial congruence among individual gene trees with inferences from eight genes placing Gonorynchus as the sister lineage to all other gonorynchiforms. Seven gene trees resolve Cromeria and Grasseichthys as a clade, supporting previous inferences using morphological characters. Phylogenies resulting from either concatenating the nuclear genes, performing a multispecies coalescent species tree analysis, or combining the morphological and nuclear gene DNA sequences resolve Gonorynchus as the living sister lineage of all other gonorynchiforms, strongly support the monophyly of Cromeria and Grasseichthys, and resolve a clade containing Parakneria, Cromeria, and Grasseichthys. The morphological dataset, which includes 13 gonorynchiform fossil taxa that range in age from Early Cretaceous to Eocene, was analyzed in combination with DNA sequences from the nine nuclear genes and a relaxed molecular clock to estimate times of evolutionary divergence. This "tip dating" strategy accommodates uncertainty in the phylogenetic resolution of fossil taxa that provide calibration information in the relaxed molecular clock analysis. The estimated age of the most recent common ancestor (MRCA) of living gonorynchiforms is slightly older than estimates from previous node dating efforts, but the molecular tip dating estimated ages of Kneriinae (Kneria, Parakneria, Cromeria, and Grasseichthys) and the two paedomorphic lineages, Cromeria and Grasseichthys, are considerably younger.
authors.affiliation: Department of Ecology & Evolutionary Biology and Peabody Museum of Natural History, Yale University, New Haven, CT 06520, USA. Electronic address: thomas.near@yale.edu.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Near
authors.affiliation: Department of Ecology & Evolutionary Biology and Peabody Museum of Natural History, Yale University, New Haven, CT 06520, USA.
authors.forename: Alex
authors.initials: A
authors.lastname: Dornburg
authors.affiliation: Department of Earth Sciences, University of Oxford, Oxford OX1 3AN, United Kingdom.
authors.forename: Matt
authors.initials: M
authors.lastname: Friedman
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D005075:Biological Evolution; D002467:Cell Nucleus / Q000235:genetics; D004272:DNA, Mitochondrial / Q000235:genetics; D005399:Fishes / Q000145:classification* / Q000235:genetics; D005580:Fossils; D008957:Models, Genetic; D010802:Phylogeny; D017422:Sequence Analysis, DNA
chemical_list: D004272:DNA, Mitochondrial
keywords: Actinopterygii; Fossil dating; Gonorynchiformes; Molecular clock; Tip dating