Patterns of Intra- and Interspecies Genetic Diversity in Klamath River Basin Suckers

Abstract

The Klamath River basin, Oregon, is home to four catostomid species: The Klamath smallscale sucker Catostomus rimiculus, the Klamath largescale sucker Catostomus snyderi, the shortnose sucker Chasmistes brevirostris, and the Lost River sucker Deltistes luxatus. A decline in Lost River and shortnose sucker abundances resulted in these species being listed as endangered under the U.S. Endangered Species Act in 1988. The primary aims of this study were to measure interspecific and intraspecific genetic variation in Klamath River basin suckers by examining 15 microsatellite loci. Over 300 suckers were sampled from four subbasins within the Klamath River basin (Lost River, upper Klamath–Sprague rivers, lower Klamath River, and upper Williamson River) and one region outside of the basin (Rogue River). A hierarchical analysis of population subdivision based on groups generated from microsatellite genetic distance (R _ST) data was performed by use of analysis of molecular variance. Assignment of individuals to known populations was performed with the program WHICHLOCI. The program STRUCTURE was used to assign individuals probabilistically to homogeneous clusters without population or species identifiers. Klamath smallscale and Lost River suckers were genetically distinct from each other and from shortnose and Klamath largescale suckers. Sympatrically occurring shortnose and Klamath largescale suckers from the Lost and upper Klamath–Sprague River subbasins were genetically indistinguishable from one another, which indicates that interspecific hybridization has occurred between these two species. Managing for the long-term survival and recovery of endangered Klamath River basin suckers should focus on preserving the genetic diversity of all four sucker species. Continued protection of endangered shortnose suckers requires the protection of Klamath largescale suckers, since each of these species may be a crucial contributor to the evolutionary legacy of the other. Maintenance of healthy and abundant sucker spawning and rearing habitat should minimize the chance of losing genetically unique populations while maintaining genetically diverse populations and facilitating the recovery of all Klamath River basin suckers.