Phylogenetic divergence in leatherside chub (Gila copei) inferred from mitochondrial cytochrome b sequences

We examined intra-specific phylogenetic relationships in leatherside chub, Gila copei. The complete mitochondrial (mt) cytochrome b gene (1140 bp) was sequenced for 30 individuals from 10 populations that span the geographica l distribution of this species. Traditional phylogenetic analyses revealed two deeply divergent and evolutionarily distinct mtDNA clades that are geog raphically separated in northern and southern drainage basins. Interpopulat ion sequence variation between clades ranged from 7.7 to 8.1%. The northern clade was genetically more similar and phylogenetically more closely relat ed to the selected out-group Lepidomeda m. mollispinus than to the southern clade, suggesting that the taxonomy of this species may require revision. Sequence variation among populations within clades ranged from 0 to 0.3% in the north and from 0 to 0.7% in the south. Statistical parsimony was used to construct phylogenetic networks of haplotypes within clades. Nested clad e analysis revealed that geographical fragmentation has played an important role in genetic structuring within northern and southern clades.