DYNAMIC GENE CONSERVATION FOR UNCERTAIN FUTURES

Programs for conserving genes in forest trees should be based on evolutionary concepts. Our recommendations for gene conservation are appropriate for conditions of rapid environmental change such as might occur under accumulation of greenhouse gases. We describe the impact that the evolutionary forces of selection, migration and genetic drift have on the genetic architecture of tree species and emphasize that maximum fitness for all traits will never be obtained in any plant population. Genetic variation is a prerequisite for future evolution and we stress that gene conservation programs should provide opportunities for future evolution. Two methods have been developed to manage populations for this purpose. One is hierarchical; in it useful genes are intended to be gradually transferred by crossing from lower to higher levels of improvement. The second, the multiple population breeding system, generates the sizeable genetic variance that is necessary to cope with future uncertainties regarding environmental conditions and trait values. We recommend this latter system whenever financing allows. Existing adaptations should be used when populations are appointed as gene resource populations. The multiple breeding population system was developed to incorporate ex situ gene conservation as an integral part of breeding. However, its basic premise of broadening among-population variance can also be accomplished in in situ programs by choosing widely varying stands as gene resource populations and diversifying them further through selection.