Genetic variation of western larch in British Columbia and its conservation

Abstract

The extent and pattern of genic variability at 20 allozyme loci were estimated in nine populations representing the British Columbia natural range of western larch (Larix occidentalis Nutt.). In addition, an attempt was made to identify genetically unique populations for conservation efforts. Heterozygosity parameters [number of alleles per locus (1.8), percent polymorphic loci (58), and average expected heterozygosity (H(e); 0.188)] indicated that the species harbors levels of genetic variation comparable to other wide-ranging, long-lived, outcrossing, wind-pollinated species. Levels of genetic variability in the British Columbia populations were higher than their American counterparts. Among-population differentiation (G(ST)) accounted for a significant 7% of the total variation. Correlation between the genetic and geographic distances was highly significant (P < .01), indicating that geographically close populations tended to be genetically similar. Genetically unique populations were identified by 'jackknife' analysis, which excluded one population at a time and compared the resultant average genetic distance (D̄), G(ST), and gene flow (Nm) of the analysis with the original analysis conducted on all nine populations. Two populations were identified to be genetically unique and were recommended for consideration for conservation efforts.