Comparative analysis of the genetic composition of canopy and Juvenile sugar mapie individuals (Acersaccharum) in an old-growth forest in southern Quebec as related to anthropogenic disturbance

The unexpected discovery of a relatively undisturbed presettlement forest in southern Quebec, the Muir Forest, allowed us to investigate the potential reproductive effects of recent man-made air pollution upon the genetic structure and variability of sugar maple (Acersaccharum Marsh.) at this site. The genetic structure of the canopy subpopulation consisting of 62 trees over 140 years of age was compared with that of three understory subpopulations of 90 juvenile individuals, 6 to 15 years old. The genetic structure and variability were analyzed using cellulose acetate electrophoresis of 14 enzyme systems. The analysis of 20 loci showed an average polymorphism of 60.1%, a mean of 1.83 alleles per locus, a mean of 1.17 effective alleles, and observed and expected levels of heterozygosity of 0.136 and 0.148, respectively. There were no significant differences among the canopy and the three juvenile subpopulations for these five genetic parameters. Estimated Fis and Fit (Wright's fixation indices) values ind...