Does genetic rescue disrupt local adaptation? An experimental test using thermally adapted Tribolium castaneum lines

Anthropogenic drivers are restricting many species to small, genetically isolated populations. These are prone to inbreeding depression and are at an increased risk of extinction. Genetic rescue, the controlled introduction of genetic variation from another population, can alleviate inbreeding effects. A major conservation concern restricting the use of this technique is that such augmented gene flow may disrupt local adaptation crucial to a population's persistence. Using populations of the red flour beetle (Tribolium castaneum) experimentally adapted to reproduce at higher temperatures, we assess whether genetic rescue attempts disrupt thermal adaptation. Rescuers, drawn from populations adapted to either 30°C or 38°C, were introduced into populations adapted to 38°C, which had been inbred for two generations. We recorded population productivity for three generations post-rescue, in the adapted 38°C environment. Rescuers with and without local adaptation significantly increased the productivity of recipient inbred populations, but those sharing local adaptation to reproduction at 38°C provided greater increases in productivity. These results show that while rescue with non-locally adapted individuals may improve productivity, having the same adaptation in rescuing individuals and rescuee populations may be important in maximizing conservation outcomes.