David Marques, me and colleagues, published a paper in PloS Genetics elucidating patterns of genomic differentiation between migratory lake and resident stream ecotypes of threespine stickleback reproducing in sympatry in one stream, and in parapatry in another stream. These ecotypes started diverging less than 150 years ago but already multiple genomic regions show signatures of adaptive genomic differentiation resisting the homogenizing effect of gene flow.