Phylogenetics of Scaphirhynchus based on mitochondrial DNA sequences

Species delineation and taxonomy within the sturgeon genus Scaphirhynchus i s controversial. This issue is made more complex by political issues regard ing the Alabama sturgeon S, suttkusi and potential hybridization between sy mpatric shovelnose sturgeon S. platorynchus and pallid sturgeon S, albus. W e investigated phylogenetic relationships among species of Scaphirhynchus b ased on nucleotide sequences for two mitochondrial loci, cytochrome b and t he control region (D-loop). White sturgeon Acipenser transmontanus and gree n sturgeon A. medirostris were used as outgroups. Phylogenetic analyses did not recover monophyletic shovelnose or pallid sturgeon; however, some popu lations of pallid sturgeon were resolved as sister to the Alabama sturgeon, and one specimen of shovelnose sturgeon was consistently resolved as the s ister to all other in group taxa. The hierarchical pattern of relationships produced by analysis of mitochondrial DNA is not consistent with that prod uced by morphological data. It is consistent with the hypothesis of a low r ate of evolution of these genes in Scaphirhynchus and reflects recent hybri dization between shovelnose and pallid sturgeon, probably due to habitat de gradation.