Increased genetic differentiation in house sparrows after a strong population decline: From panmixia towards structure in a common bird

► Population genetics of declined Finnish house sparrows was studied. ► We compared 12 populations prior and after the major population decline. ► Genetic variation was hardly lost, but population differentiation had increased. ► This may indicate a non-equilibrium situation and future loss of genetic diversity. ► Decline in a common species can also leave a genetic imprint and warrant conservation concern.