Cover Image

HARDBACK
$59.00



View/Hide Left Panel
FIGURE 1-3 A cartoon version of genomic heterogeneity of gene exchange and genetic divergence under divergent selection. One chromosome from each specialized parental population is shown, with the genomic regions that contain locally adapted genes (QTL) indicated in boxes shaded to correspond to the specialized parent from which it came. Bidirectional arrows indicate gene exchange, with the pattern in the arrow tips showing that alleles from the other population are introgressing. Gene exchange can occur outside the regions containing the specialized genes, but is blocked from occurring within those regions for the reasons shown in Fig. 1.2B. This heterogeneous pattern of gene exchange under selection establishes the genetic mosaic of speciation, in which genetic divergence is restricted to divergently selected portions of the genomes, while other regions share polymorphisms freely through ongoing gene exchange.

FIGURE 1-3 A cartoon version of genomic heterogeneity of gene exchange and genetic divergence under divergent selection. One chromosome from each specialized parental population is shown, with the genomic regions that contain locally adapted genes (QTL) indicated in boxes shaded to correspond to the specialized parent from which it came. Bidirectional arrows indicate gene exchange, with the pattern in the arrow tips showing that alleles from the other population are introgressing. Gene exchange can occur outside the regions containing the specialized genes, but is blocked from occurring within those regions for the reasons shown in Fig. 1.2B. This heterogeneous pattern of gene exchange under selection establishes the “genetic mosaic of speciation,” in which genetic divergence is restricted to divergently selected portions of the genomes, while other regions share polymorphisms freely through ongoing gene exchange.

USING FstOUTLIER ANALYSIS TO IDENTIFY SELECTED GENOMIC REGIONS IN THE GENETIC MOSAIC

Wright’s Fst is a widely used measure of genetic divergence between populations (Hartl and Clark, 1997). Lewontin and Krakauer (1973) proposed that genetic markers with aberrantly high Fst values (“outliers”) could be inferred to be affected by divergent selection. Recently, outlier analyses have enjoyed a renaissance because of the development of new methods based on coalescent simulation (Beaumont and Nichols, 1996; Beaumont and Balding, 2004). Fst variation is still used to eliminate selected markers from population genetic analyses that require neutrality (Luikart et al., 2003), but it is now of primary interest as a signature of divergent selection that permits detection of genomic regions involved in adaptive divergence (Beaumont, 2005; Storz, 2005).

Significant heterogeneity in marker Fst has been documented between ecologically divergent races (Wilding et al., 2001; Emelianov et al., 2004; Rogers and Bernatchez, 2005; Bonin et al., 2006; Oetjen and Reusch, 2007), with the interpretation that Fst outliers must be linked to loci affecting the phenotypic traits known to distinguish the divergent ecotypes, races, or subspecies. However, outlier analysis alone cannot reveal the cause of deviant Fst values, and the conclusion that Fst outliers must be associ-



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement