Conservation genetics of bull trout: Geographic distribution of variation at microsatellite loci.

Abstract

We describe the genetic population structure of 65 bull trout (Salvelinus confluentus) populations from the northwestern United States using four microsatellite loci. The distribution of genetic variation as measured by microsatellites is consistent with previous allozyme and mitochondrial DNA analysis. There is relatively little genetic variation within populations (H_S = 0.000 – 0.404, average H_S = 0.186, but substantial divergence between populations (F_ST = 0.659). In addition, those populations that had low genetic variation for allozymes also tended to have low genetic variation at microsatellite loci. Microsatellite analysis supports the existence of at least three major genetically differentiated groups of bull trout: (1) "Coastal" bull trout populations, (2) "Snake River" populations, which also include the John Day, Umatilla, and Walla Walla Rivers and, (3) populations from the upper Columbia River, primarily from the Clark Fork basin.Within the major assemblages, populations are further subdivided, primarily at the river basin level. Most of the genetic similarities we have detected probably reflect patterns of historic isolation and gene flow. However, in some cases, genetic drift and low levels of variation appear to have influenced the relationships inferred from these data. Finally, we suggest using a hierarchical approach to direct management actions in species such as bull trout for which most of the genetic variation exists among populations and local populations in close proximity typically are genetically distinct.

Citation

Spruell, P.; Hemmingsen, A.R.; Howell, P.J.; Kanda, N.; Allendorf, F.W. 2003. Conservation genetics of bull trout: Geographic distribution of variation at microsatellite loci. Conservation Genetics. 4: 17-29