isolation with migration
Pinho C & Hey J 2010 Divergence with gene flow: models and data. Annu Rev Ecol Evol Syst 41:215-230.
- gene flow mapping: identifying targets of disruptive selection by studying gene flow
- if it is found that gene flow has occurred, then the investigator is placed in the paradoxical but useful position of studying the forces driving divergence by identifying loci that have not diverged
- the investigator may not be able to identify or directly study those loci most targeted by selection
- by studying the gene exchange at other loci, the action of disruptive selection can be revealed
- evaluating which loci have experienced gene exchange and which have not can help to identify genomic locations that are contributing more than the average to divergence
- gene flow can cause a high variance in divergence among loci
- in some cases a pattern of extreme variation among genes in levels of divergence may be so striking that a conclusion of gene exchange seems warranted even without the benefit of statistics
- such seems to be the case for the M and S forms of Anopheles gambiae
- a genome-wide study showed that most of the genome has been homogenized through gene flow between the two forms, except for three small "islands" of differentiation, which are thought to contain genes that are important in keeping these forms distinct in sympatry
