A universal mechanism generating clusters of differentiated loci during divergence-with-migration

Genome-wide patterns of genetic divergence reveal mechanisms of adaptation under gene flow. Empirical data show that divergence is mostly concentrated in narrow genomic regions. This pattern may arise because differentiated loci protect nearby
mutations from gene flow, but recent theory suggests this mechanism is insufficient to explain the emergence of concentrated
differentiation during biologically realistic timescales. Critically, earlier theory neglects an inevitable consequence of genetic drift:
stochastic loss of local genomic divergence. Here, we demonstrate that the rate of stochastic loss of weak local differentiation
increases with recombination distance to a strongly diverged locus and, above a critical recombination distance, local loss is faster
than local “gain” of new differentiation. Under high migration and weak selection, this critical recombination distance is much
smaller than the total recombination distance of the genomic region under selection. Consequently...