Pike and salmon as sister taxa: Detailed intraclade resolution and divergence time estimation of Esociformes + Salmoniformes based on whole mitochondrial genome sequences

• We examined the mitogenomic relationships of Esociformes and Salmoniformes.
• The nearest relatives of Esociformes + Salmoniformes are unclear.
• Within Esociformes, these data support a single family, Esocidae.
• The subfamily relationships of Salmonidae remain unresolved by mitogenomic data.

The increasing number of taxa and loci in molecular phylogenetic studies of basal euteleosts has brought stability in a controversial area. A key emerging aspect to these studies is a sister Esociformes (pike) and Salmoniformes (salmon) relationship. We evaluate mitochondrial genome support for a sister Esociformes and Salmoniformes hypothesis by surveying many potential outgroups for these taxa, employing multiple phylogenetic approaches, and utilizing a thorough sampling scheme. Secondly, we conduct a simultaneous divergence time estimation and phylogenetic inference in a Bayesian framework with fossil calibrations focusing on relationships within Esociformes + Salmoniformes. Our dataset supports a sister relationship between Esociformes and Salmoniformes; however the nearest relatives of Esociformes + Salmoniformes are inconsistent among analyses. Within the order Esociformes, we advocate for a single family, Esocidae. Subfamily relationships within Salmonidae are poorly supported as Salmoninae sister to Thymallinae + Coregoninae.