Phylogenetic relationships of extant esocid species (Teleostei: Salmoniformes) based on mophological and molecular characters

The phylogenetic relationships of extant species of Esox were investigated using both morphological and molecular data. The complete mtDNA cytochrome b gene (cytb) and the second intron of the RAG1 gene were sequenced from multiple specimens of each species and analyzed using maximum parsimony and maximum likelihood. The resulting cladograms were compared with each other and to the morphological cladogram for congruence. Data from all three sources strongly support the monophyly of the genus, and the monophyly of the subgenera Esox (i.e., pikes) and Kenoza (i.e., pickerels). Our data support the sister-group relationship between Esox reicherti and Esox lucius (the Amur and Northern Pike, respectively). Incongruent results between the morphological and RAG1 data and the cytb data, with respect to pickerel interrelationships, suggest hybridization and introgression among pickerel species. Additional research is necessary to explore these results further. This study represents the first study to integrate both morphological and molecular data into a phylogenetic analysis of Esox. It aims to provide a better understanding of esocid evolution and lay the foundation for the interpretation of fossil material assigned to Esox. It also provides preliminary genetic evidence of hybridization among the pickerels.