Managing genetic resources of lodgepole pine in west-central Alberta: patterns of isozyme variation in natural populations and effects of forest management

Needle tissue, collected from 30 individuals in each of 57 stands of lodgep ole pine from west-central Alberta, Canada, was analyzed by starch gel elec trophoresis for eight enzyme systems encoding 12 putative loci, which displ ayed a total of 51 allozymes. In unmanaged (fire-origin, unthinned) stands there were no differences in genetic diversity among elevations (breeding r egions) and there was no relationship between geographic distance and genet ic identity. Ordination of allelic frequencies showed that there was little population differentiation related to elevation or management prescription . For harvest-origin stands there were no significant differences in geneti c diversity between regeneration methods (natural regeneration versus plant ing); nor was there any effect of pre-commercial thinning on genetic divers ity of fire- or harvest-origin stands. Harvest-origin stands had significan tly lower average population genetic diversity than unmanaged (fire-origin, unthinned) stands (expected heterozygosity, H-exp; effective number of all eles, n(e)) and also showed lower total expected (H-T) (6% less) and observ ed heterozygosity (H-O) (9% less). Unmanaged (fire-origin, naturally regene rated, unthinned) stands had significantly greater H-exp and n(e) than harv est-origin (unthinned) stands of similar age that were planted. For the hig h elevation breeding region harvest-origin stands showed lower allelic rich ness than average for a similar sample size of stands from the region; this was due mainly to missing rare (frequency <0.05) alleles. Compared to aver age values for unmanaged stands in the high elevation breeding region, 106 selected individuals from the tree improvement program for this region show ed lower H-T (15%), H-O (15%), alleles per locus (2.25 versus 4.00) and % p olymorphic loci (42% versus 75%) and were missing 47% of all alleles and 78 % of rare alleles. (C) 2001 Elsevier Science B.V. All rights reserved.