How many, and when? Optimising targeted gene flow for a step change in the environment

Abstract

Targeted gene flow is an emerging conservation strategy that involves translocating individuals with particular traits to places where they are of benefit, thereby increasing a populations evolutionary resilience. While the idea can work in theory, questions remain as to how best to implement it. Here, we vary timing of introduction and size of the introduced cohort to maximise our objective - survival of the recipient populations genome. We demonstrate our approach using the northern quoll, an Australian marsupial predator threatened by the toxic cane toad. We highlight a general trade-off between maintaining a local genome and reducing population extinction risk, but show that key management levers can optimise this so that 100% of the populations genome is preserved. In our case, any action was better than not acting at all (even with strong outbreeding depression), but the size of the benefit was sensitive to timing and size of the introduction.