Genetic variability among and within closely spaced populations of lodgepole pine
The genetic composition of Pinus contorta var. latifolia as determined by isozyme analysis was assessed and examined at two hierarchical levels; within closely spaced populations and within adjacent subpopulations. Four populations of lodgepole pine consisting of 125 trees each were sampled along an elevational gradient spanning a distance of approximately 2 km in the Front Range of the Rocky Mountains in Colorado. Each population was further divided into five subpopulations. Four isozymes were electrophoretically resolved from needle tissue removed from each tree. Statistics characterizing the genetic structure were calculated including measures of genetic variability, tests of allelic heterogeneity, and F statistics. The results indicate that lodgepole pine has a relatively low level of genetic variation with 44% of its loci polymorphic, an average of 1.33 alleles per locus, heterozygous at 13.5% of their loci, and a polymorphic index of 0.144. Slightly less than 1% of the observed genetic variability resided among the four populations with the remainder residing among the individuals within populations. A slight deficiency of heterozygotes was indicated by the F statistics analysis. Allelic distributions at the subpopulation level indicated that clustering was evident although not a predominant characteristic of the genetic pattern. It is suggested that inbreeding and (or) the pooling of individuals from different breeding groups are likely phenomena contributing to the genetic pattern in lodgepole pine over microgeographical distances.Key words: genetic variability, lodgepole pine, Pinus contorta var. latifolia, isozyme.