Restoration demography and genetics of plants: when is a translocation successful?

Abstract

Restorations are complex, often involving restoring ecological processes, vegetation structure, and species’ populations. One component of restorations is translocation of key species. Translocations (introductions, reintroductions, augmentations) are often necessary to recover species diversity and install key species. In this review, I consider the ways translocations have been evaluated at various stages during the process of restoration. Vital rates (survival, growth, fecundity) of propagules (seeds, transplants) are commonly used to evaluate initial success. Transplants usually provide greater initial success than do sown seeds. Beyond initial rates, completion of the life cycle through flowering, fruiting, dispersal and subsequent seedling recruitment is a key benchmark. Modelling population viability of translocated populations is a logical next step and can bring in many powerful inferential tools. Of factors affecting the success of translocations, genetic issues are paramount, as restorationists need to consider inbreeding depression, reproductive viability, local adaptation, and evolutionary potential of translocated populations. The success of translocations is also clearly context-dependent, with herbivory, disturbance, competition and other ecological factors important. Future translocations need to make better use of comparisons with reference populations, a long-term perspective on success and an experimental framework that can provide both practical and basic knowledge. Demographic data collection and analysis in restorations has great potential to elucidate causes of translocation failure and improve the prognosis of future restorations.