Among-Locus Variation in F_st: Fish, Allozymes and the Lewontin-Krakauer Test Revisited

Corresponding author: Charles F. Baer, Colorado State University, Ft. Collins, CO 80523-1878., cbaer{at}lamar.colostate.edu (E-mail)

Communicating editor: M. SLATKIN

Variation among loci in the distribution of allele frequencies among subpopulations is well known; how to tell when the variation exceeds that expected when all loci are subject to uniform evolutionary processes is not well known. If locus-specific effects are important, the ability to detect those effects should vary with the level of gene flow. Populations with low gene flow should exhibit greater variation among loci in F_st than populations with high gene flow, because gene flow acts to homogenize allele frequencies among subpopulations. Here I use Lewontin and Krakauer's k statistic to describe the variance among allozyme loci in 102 published data sets from fishes. As originally proposed, k >> 2 was considered evidence that the variation in F_st among loci is greater than expected from neutral evolution. Although that interpretation is invalid, large differences in k in different populations suggest that locus-specific forces may be important in shaping genetic diversity. In these data, k is not greater for populations with expected low levels of gene flow than for populations with expected high levels of gene flow. There is thus no evidence that locus-specific forces are of general importance in shaping the distribution of allele frequencies at enzyme loci among populations of fishes.

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