title: Phylogenetic status and timescale for the diversification of Steno and Sotalia dolphins.
abstract: Molecular data have provided many insights into cetacean evolution but some unsettled issues still remain. We estimated the topology and timing of cetacean evolutionary relationships using bayesian and maximum likelihood analyses of complete mitochondrial genomes. In order to clarify the phylogenetic placement of Sotalia and Steno within the Delphinidae, we sequenced three new delphinid mitogenomes. Our analyses support three delphinid clades: one joining Steno and Sotalia (supporting the revised subfamily Stenoninae); another placing Sousa within the Delphininae; and a third, the Globicephalinae, which includes Globicephala, Feresa, Pseudorca, Peponocephala and Grampus. We also conclude that Orcinus does not belong in the Globicephalinae, but Orcaella may be part of that subfamily. Divergence dates were estimated using the relaxed molecular clock calibrated with fossil data. We hypothesise that the timing of separation of the marine and Amazonian Sotalia species (2.3 Ma) coincided with the establishment of the modern Amazon River basin.
authors.affiliation: Departamento de Genética, Instituto de Biologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Haydée A
authors.initials: HA
authors.lastname: Cunha
authors.forename: Lucas C
authors.initials: LC
authors.lastname: Moraes
authors.forename: Bruna V
authors.initials: BV
authors.lastname: Medeiros
authors.forename: José
authors.initials: J
authors.lastname: Lailson-Brito
authors.forename: Vera M F
authors.initials: VM
authors.lastname: da Silva
authors.forename: Antonio M
authors.initials: AM
authors.lastname: Solé-Cava
authors.forename: Carlos G
authors.initials: CG
authors.lastname: Schrago
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D005075:Biological Evolution; D002138:Calibration; D002591:Cetacea / Q000502:physiology*; D004272:DNA, Mitochondrial / Q000235:genetics; D004289:Dolphins; D019143:Evolution, Molecular; D054629:Genome, Mitochondrial; D016013:Likelihood Functions; D008954:Models, Biological; D015233:Models, Statistical; D008969:Molecular Sequence Data; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D013020:South America; D013997:Time Factors
chemical_list: D004272:DNA, Mitochondrial