Abstract
The pallid sturgeon (Scaphirhynchus albus), which is protected under the US endangered species act, and shovelnose sturgeon (S. platorhynchus), which is legally harvested in some locations, are sympatric throughout the range of pallid sturgeon. There is considerable morphological overlap between the species making discrimination problematic. The inability to reliably differentiate between species across all life stages has hampered pallid sturgeon recovery efforts. Furthermore, the two species are believed to hybridize. This study used allele frequency data at multiple microsatellite loci to perform Bayesian and likelihood-based assignment testing and morphological measures and meristics to discriminate pallid, shovelnose, and putative hybrid sturgeons from the middle Mississippi River. Bayesian model-based clustering of the genetic data indicated that two natural genetic units occur in the region. These units correspond to morphologically identified pallid and shovelnose sturgeon. Some individuals were morphologically intermediate and many of these failed to strongly assign genetically as either pallid or shovelnose sturgeon, suggesting they may be hybrids. These data indicate that pallid sturgeon and shovelnose sturgeon are genetically distinct in the middle Mississippi River (F ST = 0.036, P < 0.0001) and suggest that hybridization between pallid sturgeon and shovelnose sturgeon has occurred in this region with genetic distance estimates indicating the greatest distance is between pallid and shovelnose sturgeon, while hybrid sturgeon are intermediate but closer to shovelnose. This study demonstrates that assignment testing with multiple microsatellite markers can be successful at discriminating pallid sturgeon and shovelnose sturgeon, providing a valuable resource for pallid sturgeon recovery and conservation.
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Acknowledgements
The authors would like to acknowledge the United States Fish and Wildlife Service Section 3, United States Army Corps of Engineers St. Louis District, and the North American Native Fishes Association for funding this research. The efforts of all researchers who provided samples (CEWES, MDC LTRM, SIU River Team) are greatly appreciated. Dr. P. Wills is acknowledged for his assistance and cooperation in comparing and contrasting the CI values. We thank Dr. G. Moyer and Dr. M. Bagley for reviewing an earlier draft of this manuscript, as well as three anonymous reviewers for their valuable comments.
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Schrey, A.W., Sloss, B.L., Sheehan, R.J. et al. Genetic discrimination of middle Mississippi River Scaphirhynchus sturgeon into pallid, shovelnose, and putative hybrids with multiple microsatellite loci. Conserv Genet 8, 683–693 (2007). https://doi.org/10.1007/s10592-006-9215-9
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DOI: https://doi.org/10.1007/s10592-006-9215-9