THE ORGANIZATION OF GENETIC VARIABILITY IN CENTRAL AND MARGINAL POPULATIONS OF LODGEPOLE PINEPINUS CONTORTAspp.LATIFOLIA

Abstract

A survey was conducted of genetic variation at 25 loci in extracts of individual megagametophytes of lodgepole pine. Collections were made in 9 widely separated localities representing 4 marginal, 2 intermediate and 3 central populations. Single populations of lodgepole pine were polymorphic at 58.67% of their loci, and had 1.90 alleles/locus. Both expected and observed heterozygosity averaged 0.16. There was a definite trend towards decreased genetic variability at the margins. The measures of gene diversity for the 25 loci showed a 4% but significant effect of interpopulation differentiation; 96% of the total gene diversity resided within populations. Estimated outcrossing rates (.hivin.t) for the 9 populations ranged 0.92-1.29. Comparisons among populations with different levels of outcrossing revealed no clear relationship between (.hivin.t) and amount of genetic variability. The overall pattern of genetic differentiation agrees with expectations based on the neutral mutation theory. Loci (2) demonstrated conspicuous clinal variation patterns which may be incompatible with this stochastic model.