Whitebark Pine (Pinus albicaulis)
Whitebark pine is a keystone species in high-elevation ecosystems. It has been severely impacted by white pine blister rust an introduced disease caused by the fungus Cronartium ribicola, and is at risk of local extirpation in some areas. In an earlier CFCG study (Krakowski et. al. 2003), we studied the mating system of whitebark pine in two British Columbia populations and found a lower level of outcrossing then typical for wind-pollinated conifers. For his Ph.D. project, Andy Bower has conducted a seedling common garden study to assess rangewide genetic variation in quantitative traits that may reflect local adaptation. This information will be useful in developing seed transfer guidelines for restoration plantings to avoid maladaptation. Andy has also used isozyme analysis to: 1) confirm the mating system of whitebark pine for a larger number of populations; and 2) to determine if significant inbreeding depression can be detected in quantitative traits by comparing the family mean inbreeding coefficient, calculated from the parental outcrossing rate, with family mean performance of the seedlings; and 3) determine if levels of inbreeding differ among age cohorts (seedling, sapling and mature) or among sites with different levels of blister rust infection across 14 populations. His results confirm that whitebark pine has a mixed mating system, but the outcrossing rate is higher in more southern (U.S.) populations than previously found in BC, and the mean outcrossing rate is close to the mean of other conifers (tm = 0.86). Significant inbreeding depression was only detected in one trait: total seedling biomass. There was evidence of inbreeding in seedlings, saplings and mature trees, but when the level of rust is low, the heterozygote deficiency decreases with age. When the level of rust is high, however, there is some evidence that more homozygous individuals are more likely to survive, possibly due to recessive resistance genes being expressed in more inbred individuals.