Demographic and genetic factors affect the use of translocation for evolutionary rescue: A case study of American chestnut using simulation

For many plant species at risk, recovery depends on supplementing populations with adaptive genetic diversity through translocations but specific introduction strategies for maximizing success are rarely evaluated. American chestnut ( Castanea dentata ), a North American tree species whose populations have dramatically declined due to chestnut blight (caused by Cryphonectria parasitica ), depends on evolutionary rescue to reverse its current trajectory. One approach to combating its decline is to supplement populations with more resilient genotypes (hereafter, resistant), derived from isolated individuals in natural populations or selectively bred individuals. To identify the most effective restoration strategies, we evaluated the demographic and genetic conditions supporting population recovery using American chestnut as a case study. We examined two scenarios: natural recovery without translocation and the introduction of blight‐resistant genotypes. Using existing data on chestnut demography and the genetic basis of resistance, we developed an individual‐based simulation to model population dynamics over 500 years. Our simulations indicate that evolutionary rescue is feasible but only under a restrictive set of conditions. Transplants with a high mean frequency of blight‐resistance alleles, especially when spatially clustered, significantly reduced the probability of extinction over a 500‐year period. Achieving extinction probabilities below 10% was achieved through a combination of increased recruitment rates, the number of transplants and resistance, emphasizing the critical interplay between demographic and genetic parameters for recovery. Synthesis and applications . These findings underscore the importance, complexity and flexibility of strategic translocations for ensuring the recovery of plant species limited by adaptive genetic diversity.