GENETIC-VARIATION OF THE RIPARIAN PIONEER TREE SPECIES POPULUS-NIGRA L .1. STUDY OF POPULATION-STRUCTURE BASED ON ISOZYMES

Eight polymorphic isozyme loci were used to describe the level and org anization of the genetic diversity in Populus nigra L. over 111 sites in France and among 60 additional individuals from throughout the spec ies range. Best descriptors and estimators of gene diversity and diffe rentiation were sought. Overall diversity level was found to be compar able to other widespread species. Differentiation at three geographica l scales was low, although local allele fixations indicated limitation of gene flow. Inferences were made on the effect of the natural histo ry of the species on the organization of neutral diversity, and recomm endations for collection of genetic resources were derived.