Phylogenetics of Scaphirhynchus based on mitochondrial DNA sequences

Species delineation and taxonomy within the sturgeon genus Scaphirhynchus is controversial. This issue is made more complex by political issues regarding the Alabama sturgeon S, suttkusi and potential hybridization between sympatric shovelnose sturgeon S. platorynchus and pallid sturgeon S, albus. We investigated phylogenetic relationships among species of Scaphirhynchus based on nucleotide sequences for two mitochondrial loci, cytochrome b and the control region (D-loop). White sturgeon Acipenser transmontanus and green sturgeon A. medirostris were used as outgroups. Phylogenetic analyses did not recover monophyletic shovelnose or pallid sturgeon; however, some populations of pallid sturgeon were resolved as sister to the Alabama sturgeon, and one specimen of shovelnose sturgeon was consistently resolved as the sister to all other in group taxa. The hierarchical pattern of relationships produced by analysis of mitochondrial DNA is not consistent with that produced by morphological data. It is consistent with the hypothesis of a low rate of evolution of these genes in Scaphirhynchus and reflects recent hybridization between shovelnose and pallid sturgeon, probably due to habitat degradation.