local adaptation
Barton NH 2010 Genetic linkage and natural selection. Phil Trans R Soc Lond B 365:2559-2569.
- can we really believe that natural populations are subject to the homogeneous selection envisaged by the current view of molecular evolution?
- almost all traits show high genetic variance
- their heritable variance is just as high for components of fitness
- quantitative traits typically are under strong selection in nature (directional, stabilizing and disruptive; Kingsolver et al. 2001)
- it is possible in principle that abundant heritability is maintained in a mutation–selection balance
- if so, the alleles involved would have to be under quite weak selection (s ~ Vm/Vg ~ 10− 3; Johnson & Barton 2005)
- it seems to me more plausible that changes in environment in space and time cause corresponding fluctuations in selection on the underlying alleles
- this may maintain balanced polymorphism, or may more broadly maintain a flux of alleles that leads to much higher diversity in selected alleles and traits than would arise from a static mutation–selection balance
- this view is still constrained by the puzzling constancy of the molecular clock and by the modest rate of species-wide sweeps
- local populations experience much more selected change than does the species as a whole
- if the additive genetic variance in fitness were as high as approximately 0.1, then there would be substantial HRI between even unlinked loci
- a modifier of sex or recombination would experience a more or less immediate advantage through experiencing an effectively lower rate of drift
