Effect of population outcrossing rate on inbreeding depression in Pinus contorta var. murrayana seedlings.

Abstract

Seft and cross families from three populatons (A, low-density, ecologically marginal site for lodgepole pine, and B + C, normal sites) were cultured in a common outdoor nursery for 2 yrs. Previous results results had shown higher natural selfing rates and lower inbreeding depression in embryo survival in A than in B + C. In the nursery test, selfing decreased means of size traits, retarded phenological development, increased variance among families within populations, increased the coefficient of within-family variance, and increased within-family skewness. The selfing depression of mean values was moderately less and the selfing inflation of within-plot variation was much less in A than in B + C. Results were compatible with the idea that the higher selfing rate in A had purged both severely deleterious alleles affecting embryo survival and severely deleterious deleterious alleles affecting later life-cycle traits related to plant size. Purging partially mitigated the genetic consequences associated with increased inbreeding in small populations, but even with purging, population A retained a large inbreeding depression in both embryonic and seedling traits.

Citation

Sorensen, Frank C. 2001. Effect of population outcrossing rate on inbreeding depression in Pinus contorta var. murrayana seedlings. Scandinavian Journal of Forest Research. 16: 391-403