Inbreeding depression

Inbreeding depression is the reduced biological fitness caused by loss of genetic diversity as a result of inbreeding, or mating between closely related individuals within a species. This reduction of fitness occurs because inbreeding increases genetic similarity, which can amplify harmful genes and overall decreases diversity. Inbreeding depression is often attributed to small population size, often stemming from a population bottleneck, where low genetic variation restricts a species' ability to adapt.

Biological fitness refers to an organism's capability to survive and transmit its genetic material to the next generation. Higher genetic variation within a breeding population increases the fitness and survivability of a species. Inbreeding depression appears to be present in most populations of organisms but varies across mating systems. In summary, inbreeding depression demonstrates the importance of genetic diversity within populations of species and how it contributes to natural selection.