Dynamics of genetic adaptation to captivity

Many species require captive breeding to savethem from extinction, with reintroduction intothe wild being the eventual aim of mostprograms. Adaptation to captive environmentstypically results in reduced fitness under wildconditions. Consequently, unintentionaladaptation during captive breeding programs mayseriously compromise the success ofreintroduction programs. However, there islittle experimental evidence on the rate orextent of adaptation for captive populationsmaintained under benign captive conditions forextended periods of time. To investigate thedynamics of genetic adaptation to captivity,large captive populations of Drosophilamelanogaster were assessed for relativefitness under captive conditions for up to 87generations in captivity. Captive fitnessincreased to 3.33 times the initial fitnessover 87 generations. The pattern of adaptationwas curvilinear, with an exponential curveproviding the best fit. Fitness reached 25% ofits maximum within 6 generations, 50% within15 generations, 75% within 31 generations and95% within 67 generations. The model predictedthat the asymptotic level of fitness reachedwould be 3.38 times the initial fitness. Thus,very large genetic adaptations to captivity mayoccur under relatively benign captiveconditions. Captive populations destined forreintroduction need to be managed to minimisegenetic adaptation to captivity.