What is the consequence of inbreeding in small populations?

Inbreeding in small populations can lead to inbreeding depression, which is a decline in fitness and health due to the increased likelihood of offspring inheriting harmful alleles from both parents. When closely related individuals mate, their offspring are more likely to be homozygous for deleterious genes, which can result in a higher incidence of genetic disorders, reduced fertility, and lower survival rates. This reduction in overall fitness can threaten the survival of the population, especially if the population is already small and has limited genetic diversity.

In contrast, increasing genetic diversity or improving overall fitness is generally associated with outcrossing or mating between unrelated individuals. Additionally, inbreeding does not lead to larger population sizes; in fact, it can contribute to population declines due to the aforementioned negative effects. Thus, the consequence of inbreeding in small populations is primarily characterized by inbreeding depression, where the genetic health of the population deteriorates over time.