Understanding Inbreeding Depression, Purging, and Genetic Rescue.

Inbreeding depression, the reduction of fitness caused by inbreeding, is a nearly universal phenomenon that depends on past mutation, selection, and genetic drift. Recent estimates suggest that its impact on individual fitness is even greater than previously thought. Genomic information is contributing to its detection and can enlighten important aspects of its genetic architecture. In natural populations, purging and genetic rescue mitigate fitness decline during inbreeding periods, and might be critical to population survival, thus, both mechanisms should be considered when assessing extinction risks. However, deliberate purging and genetic rescue involve considerable risk in the short and medium term, so that neither appears to be a panacea against high inbreeding depression.