Phylogenetic Relationships of Esocoid Fishes (Teleostei) Based on Partial Cytochrome b and 16S Mitochondrial DNA Sequences

The phylogenetic systematics of esocoid fishes are examined using comparisons of partial DNA sequences of the mitochondrial genes coding for the transmembrane protein cytochrome b and the 16S RNA ribosomal subunit. Nucleotide sequences from all species of umbrids, three species of esocids, and salmonid, osmerid, cypriniform, and neoteleostean outgroups were compared to determine patterns of molecular evolution and uncover evidence of phylogenetic relationships. Multiple sequence alignments for each of the two DNA regions examined were used to characterize the amount and type of change shown by the data. The sequences were analyzed under different models of molecular evolution using maximum-parsimony and maximum-likelihood optimality criteria of phylogenetic reconstruction. The phylogenetic analyses revealed previously undiscovered affinities between species of umbrids and esocids that imply the paraphyly of the Umbridae as currently defined. The following set of esocoid interrelationships is proposed: (((Esox, Novumbra), Dallia), Umbra). Esocoid classification is revised based on present findings.

Fig. 1.

Previously proposed hypotheses of esocoid relationships: (A) Cavender, 1969; (B) Nelson, 1972; (C) Reist, 1987

Fig. 2.

Cytochrome b substitution plots. Number of transitions (∘) and transversions (•) at codon positions: (A) 1, (B) 2, and (C) 3 are plotted against uncorrected percent sequence divergence for all pairwise species comparisons

Fig. 3.

Estimates of esocoid phylogeny supported by mtDNA sequence data: (A) Most-parsimonious (left and right) and maximum-likelihood (right) trees based on cytochrome b sequences. Both trees are equally parsimonious. (B) Most-parsimonious and maximum-likelihood tree based on 16S sequences. Values above tree edges are jackknife indices of support for maximum parsimony; those below tree edges are for maximum likelihood. * represent jackknife values of 100%. Nodes present on both trees have equal jackknife values

Fig. 4.

Parsimony based split-decomposition and spectral analysis graphs from Splitstree (vers. 2.4, D. H. Huson, 1997, unpubl.). Split-decomposition graphs for (A) cytochrome b and (B) 16S. Graphs are derived from uncorrected distance matrices (hamming distances)

Fig. 5.

16S substitution plot. Number of transitions (∘) and transversions (•) are plotted against uncorrected percent sequence divergence for all pairwise species comparisons. The distinct cluster of transition and transversion points at the highest levels of divergence corresponds to pairwise comparisons involving the osmerid outgroup

Fig. 6.

Consensus of (A) MP trees from 000 jackknife pseudoreplicates and (B) ML trees from 100 jackknife pseudoreplicates of the combined dataset. Values on trees correspond to percent occurrence of the clade among MP or ML trees of jackknife pseudoreplicates of the data matrices. Values above tree edges are derived from analyses on uniformly weighted data. Values below tree edges are derived from analyses where transitions at third codon positions of cytochrome b were weighted one-third relative to all other changes. Only one value is given where differential and uniform weighting yielded the same result

Accepted: 30 Sept 1999