Isolated Demes as a Genetic Management Strategy for Ex Situ Conservation Programs

A large number of freshwater fish, amphibian, and invertebrate insurance populations are managed by zoos and aquariums. Most of these species have very short generation times, which leads to the rapid loss of genetic diversity, reducing the potential to contribute to the survival of the species in the wild. We argue that these programs should consider an isolated deme strategy, where species are managed without exchange between groups. This allows genetic diversity to be maintained through isolation. The potential of such a strategy has been long understood, but there are no known cases where it has been consciously implemented. This seems mainly due to the lack of guidance on when to select it as a strategy, and how to implement it. Based on existing simulations, experiences, and experimental data, the benefits of an isolated deme strategy appear to outweigh the risks of inbreeding for r-selected species like many freshwater fish, amphibians, and invertebrates. We provide guidance for managers to assess if this strategy is appropriate and how to implement it. Acknowledging that more research is still needed, we identify opportunities for new studies that allow for better implementation of isolated deme strategies in the coming decades.