Phylogenetic Relationships Among Members ofSalvelinusInferred from Mitochondrial DNA Divergence

Abstract

Mitochondrial DNA (mtDNA) was isolated from five species of the genus Salvelinus (alpinus, confluentus, fontinalis, malma, and namaycush) and from the closely related toxin, Hucho hucho. Restriction sites recognized by 14 endonucleases were mapped for each of the species and percent sequence divergence estimated between species pairs. A phylogeny of Savelinus based on restriction analysis of mtDNA, using Hucho as an outgroup, readily resolved in three subgenera: Baione, Cristivomer, and Salvelinus. Within Baione, no differences were detected between the mtDNA of brook (S. fontinalis fontinalis fontinalis) and aurora (S. f. timagamiensis) trout. However, members of the subgenus Salvelinus were more variable such that two groups were resolved, one consisting of S. alpinus alpinus, S. a. oquassa, and S. malma, and the other of S. a. stagnalis and S. confluentus. A composite distance phenogram representing the phylogeny of the subfamily Salmoninae was constructed using the sequence divergence data obtained in the current study in conjunction with data from three other salmonid mtDNA studies. Estimates of divergence time between the major taxa of this group suggest that the salmonine genera originated in the late-Miocene to early-Pliocene, while extant species originated during the late-Pliocene to early-Pleistocene.