Bottlenecked populations: A bottlenecked population is a group of organisms that has gone through a sharp reduction in size—often due to events like habitat loss, disease, overhunting, or environmental change. This sudden reduction causes a loss of genetic diversity, because only a small number of individuals (and their genes) survive to rebuild the population. Over time, this can increase the risk of inbreeding depression and make the population less able to adapt to new threats.