Desert Fishes Council, Moab, UT, November 2010.

A mitochondrial DNA phylogeny of the mountain suckers, Pantosteus.

P.J. Unmack, D.K. Shiozawa, C.L. Secor, G.R. Smith, R.L. Mayden, T.E. Dowling

Mountain suckers (genus Pantosteus) have an interesting distribution across western North America stretching from southwestern Canada to northwestern Mexico. Essentially they straddle one of the most geologically active regions of the continent which makes them interesting in terms of the regional biogeography. Currently six species are recognized, P. clarkii Desert Sucker, P. discobolus Bluehead Sucker, P. nebuliferus Nazas Sucker, P. platyrhynchus Mountain Sucker, P. plebeius Rio Grande Sucker and P. santaanae Santa Ana Sucker. Many of these species are often sympatric with another sucker from the genus Catostomus. Sampling for each species included multiple representatives, typically covering their geographic range. Multiple outgroups were included from the genus Catostomus as well as several more distantly related suckers. Phylogenetic data was collected from nine mitochondrial genes for a total of 8055 base pairs. Both maximum likelihood and maximum parsimony produced well resolved topologies with only two minor differences. Our results confirm what others have suggested relative to the taxonomic diversity within the group being underestimated. Pantosteus platyrhynchus consisted of five lineages, two of which appear to have earlier been introgressed with P. discobolus. Three distinct lineages were also found in both P. discobolus and P. plebeius. Based on the molecular divergences, all of these distinct lineages likely deserve separate species recognition. Phylogenetically and geographically Pantosteus can be divided into three lineages. The most basal lineage consisted of P. platyrhynchus (excluding Bonneville Basin) which inhabits the northern range of the genus. The second lineage contained P. plebeius and P. nebuliferus from the southern most portion of the range of the genus. The geographically central Pantosteus species formed the third major lineage (P. santaanae, P. clarkii, P. discobolus, Bonneville P. platyrhynchus).