Phylogenetic relationships among the four currently recognized species in the genus Erimyzon were reconstructed using sequence data obtained from the mitochondrially encoded COI and the nuclear-encoded IRBP2 genes. Maximum likelihood and Bayesian analyses yielded five groups of Erimyzon. Three of the clades corresponded to the species E. oblongus, E. tenuis, and E. claviformis. Individuals identified as E. sucetta were split into two separate clades, with one clade more closely related to E. oblongus than to the other E. sucetta clade in three of four analyses. Two instances of putative hybridization between sympatrically distributed species were also detected, one involving E. oblongus and E. sucetta and the other involving E. claviformis and E. tenuis. The results suggest that the currently recognized E. sucetta comprises two species, with potentially non-overlapping distributions. Further morphological investigation is warranted to provide additional support for recognizing this putative fifth species of Erimyzon.
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