Assessing the benefits and risks of translocations in depauperate species: a theoretical framework with an empirical validation.
Conservation translocations are becoming more common to assist in the management of threatened native species. While many translocation programs focus on maximizing survival in newly established populations, consideration is also required for the persistence of source populations. Here, we present and test a theoretical framework that assesses the translocation trade-off between increasing a species probability of survival and decreasing a species' overall genetic diversity. We anticipate that (a) the genetic diversity of translocated populations will be reduced compared to the source due to a failure to capture and retain genetic diversity and (b) the genetic diversity of the source population will decline due to the removal of founder individuals. We test this framework with an empirical study of redfin blue eye Scaturiginichthys vermeilipinnis, a critically endangered fish species which has undergone several replicate translocations, established with founders sourced from a single remnant population. Several generations after reintroduction, we show that the predicted survival of the species has improved as a result of these translocations. While the species' genetic diversity has been retained across all populations combined (translocated and source), we show that genetic diversity in each individual population (including the source) is reduced compared to the source population prior to translocation. Synthesis and applications. Conservation translocations can provide great benefits to species survival, enabling extinction risk to be spread across multiple populations. Translocated populations, however, often harbour reduced genetic diversity compared to source populations and initiating translocated populations can decrease the genetic diversity of source populations, placing them at an increased risk of extinction. The framework presented here enables the trade-off between extinction risk and retention of genetic diversity to be established. This will enable the optimal conservation strategy to be employed to increase the long-term persistence and evolutionary potential of a species.