Restoration of genetic variation lost – the genetic rescue hypothesis

It has been long known that immigrants from surrounding populations might prevent the extinction of small populations, a process known as the ‘rescue effect’. This focuses on the demographic effects of migration through the direct positive influence that immigrants have on abundance of the recipient population. Now, two recent papers have indicated another potentially important way that migration might rescue populations from extinction – replenishing genetic variation and reducing inbreeding depression, or what has been termed ‘genetic rescue’.