TEMPORAL DIFFERENCES IN GENETIC DIVERSITY AND STRUCTURE OF SUGAR MAPLE IN AN OLD-GROWTH FOREST

Genetic data were collected for five developmentally based cohorts of Acer saccharum Marsh. in a large southwestern Ohio nature preserve. A minimum of 48 individuals were sampled from each of the following cohorts: embryos, 1st-year seedlings, and three diameter at breast height classes (less-than-or-equal-to 2, 15-25, and greater-than-or-equal-to 40 cm). Genotypes at eight loci were inferred from phenotypic enzyme patterns of seven enzymes extracted from cambial tissue and resolved by starch gel electrophoresis. Allelic data were subdivided by cohort and statistically compared. There was no significant difference in observed heterozygosity among the cohorts. Nei's gene diversity statistics, Nei's unbiased genetic distance, and chi2 analyses of allele and genotype frequency heterogeneity indicated that there was little genetic differentiation among cohorts. The observed differentiation resulted from allele and genotype frequency differences between seedlings and other cohorts.