Scaphirhynchus Conference: Alabama, Pallid, and Shovelnose Sturgeon

St. Louis, Missouri, 11-13 January 2005

1.  HOW MANY SPECIES OF SCAPHIRHYNCHUS ARE THERE?  NORTH AMERICAN STURGEON BIODIVERSITY ACCORDING TO THE EXPERTS

Richard L. Mayden*, Department of Biology, St. Louis University, 128 Macelwane Hall, 3507 Laclede Avenue, St. Louis, MO 63103-2010; Phone 314-977-3494; FAX 314-977-3658; maydenrl@slu.edu

Bernard R. Kuhajda, Department of Biological Sciences, University of Alabama, Box 870345, Tuscaloosa, AL 35487-0345; Phone 205-348-1822; FAX 205-348-6460; bkuhajda@bama.ua.edu

Robert M. Wood, Department of Biology, St. Louis University, 128 Macelwane Hall, 3507 Laclede Avenue, St. Louis, MO 63103-2010; Phone 314-977-3904; FAX 314-977-3658; wood2@slu.edu

Currently, there are three species of Scaphirhynchus recognized by systematic and taxonomic ichthyologists: Pallid Sturgeon, S. albus; Shovelnose Sturgeon, S. platorynchus; and Alabama Sturgeon, S. suttkusi.  All three of these species are diagnosable from one another with morphological characters, some of which don’t even require the use of sight, as well as life history and behavioral characteristics.  Despite a solid scientific basis for these three species representing distinct evolutionary lineages, some have questioned the existence of more than one or two species of Scaphirhychus in North America. 

With the description and prompt protection of the Federally Endangered Alabama Sturgeon came a variety of unpublished opinions and one non-peer reviewed publication questioning this sturgeon as a distinct species.  Likewise, the hypothesized hybridzation between the Pallid and Shovelnose Sturgeon where the two species have come into contact has caused others to question the validity of these two species if they are interbreeding, especially under the Biological Species Concept.  Addressing both of these issues with the use of molecular tools has revealed that there is limited divergence between all three species at the molecular level for the few genes analyzed thus far.  Furthermore, many of the studies that have been done to date on Pallid and Shovelnose sturgeon genetics have yet to reveal diagnostic genetic markers for the species, though all of these studies have been compromised because of poor metrics used in species identification when obtaining critical tissues. 

Thus, there been both politically motivated reasons and some empirical evidence from current molecular data that has lead some to question the validity of the three morphologically-distinct sturgeon species of Scaphirhynchus in North America.  We argue that the currently recognized species are valid and that the politically motivated arguments to the contrary are not grounded in any scientific merit and have no place in the discussion of diversity of sturgeon.  The lack of diagnostic molecular characters at a limited number of genes is of no relevance to the question of these taxa representing evolutionary species because other diagnostic traits already exist.  While it would make hatchery, propagation, and forensic efforts easier if there were unique molecular markers for the Pallid and Shovelnose Sturgeon (they exist for Alabama Sturgeon), such an inconvenience to some is not relevant to the question of diversity and does not provide falsification of the existing morphological, ecological, and behavioral divergences between these three species.