Genetic rescue in Isle Royale wolves: genetic analysis and the collapse of the population

While genetic rescue is known to benefit population viability, the duration of that benefit is poorly understood. We document what appears to be the waning benefit of genetic rescue after approximately 2-3 generations for the wolf population in Isle Royale National Park. The fitness benefit of genetic rescue declined because of inbreeding and population abundance declined when the inbred individuals exhibited low reproduction and survival. Only detailed studies of other cases will reveal what aspects of these dynamics represent general features of genetic rescue. We also present evidence indicating that numerous past immigration events have likely gone undetected. This finding is of particular significance because the Isle Royale wolf population has maintained good population viability for decades even though it was small and thought to be isolated from the mainland population of wolves. Past gene flow also suggests that human-assisted gene flow is necessary to conserve the ecosystem services associated with predation, since climate warming has reduced the frequency of ice bridges and with it the only opportunity for unassisted gene flow.