Genetics and extinction

The role of genetic factors in extinction has been a controversial issue, especially since Lande's paper [Genetics and demography in biological conservation, Science 241 (1988) 1455-1460] paper in Science. Here I review the evidence on the contribution of genetic factors to extinction risk. Inbreeding depression, loss of genetic diversity and mutation accumulation have been hypothesised to increase extinction risk. There is now compelling evidence that inbreeding depression and loss of genetic diversity increase extinction risk in laboratory populations of naturally outbreeding species. There is now clear evidence for inbreeding depression in wild species of naturally outbreeding species and strong grounds from individual case studies and from computer projections for believing that this contributes to extinction risk. Further, most species are not driven to extinction before genetic factors have time to impact. The contributions of mutation accumulation to extinction risk in threatened taxa appear to be small and to require very many generations. Thus, there is now sufficient evidence to regard the controversies regarding the contribution of genetic factors to extinction risk as resolved. If genetic factors are ignored, extinction risk will be underestimated and inappropriate recovery strategies may be used.