Genetic diversity
Genetic diversity in a population is dependent on the cumulative effects of mutation, natural selection, and population size over many generations. The effective population size ("Ne") is the number of individuals in a given population that are able to reproduce and contribute offspring to the next generation. Genetic diversity decays over generations at a rate that is inversely related to the effective population size. In small populations, a major factor that causes a loss of genetic diversity is inbreeding. Intentionally breeding for desirable attributes in a species is known as selective breeding. This process artificially limits the size of the population pool, thereby increasing the rates of inbreeding as well as inbreeding depression, and decreasing a species biological fitness.