Genetic Diversity, Differentiation and Mating System in Mountain Hemlock (Tsuga mertensiana) Across British Columbia

2000

S. 97-108

4 Abb., 5 Tab., 38 Lit. Ang.

Unselbständiges Werk

200069742

Genetic diversity, mating system and evlutionary history of 19 populations of mountain hemlock (Tsuga mertensiana) within British Columbia were inferred from genetic variation at 19 allozyme loci. Within populations, 32 % of the loci were polymorphic and expected heterozygosity was 0.087, which is ca. half the heterozygosity found in other conifers. Outcrossing rates did not significantly differ from 100 %. Populations showed moderate differentiation (Gst = 0.077), island populations showed considerably more differentation (Gst = 0.095) than mainland populations (Gst = 0.058), and an isolation-by-distance analysis suggests restricted gene flow. For the populations ins southwestern British Columbia, there was a significant positive correlation between average expected heterozygosity and elevation, while expected heterozygosity was negatively correlated with latitude. This suggests that during a northward post-glacial range expansion, more northerly mountain hemlock populations suffered a loss in genetic variation due to this migration.