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Whitebark pine (Pinus albicaulis Engelm.) is threatened across its native range by an exotic fungal pathogen introduced within the last century. Mortality has been extensive, and projected potential range shifts based on impending climate change have revealed further pressures to survival and adaptation for this long-lived, high-elevation conifer. Quantifying genetic variation and the mating system of whitebark pine in its northern range provides a basis for effective conservation measures. Isozyme analysis of vegetative bud tissue revealed high expected heterozygosity (0.262), moderate population differentiation (FST = 0.061) and highly significant correlations between observed heterozygosity and geographic variables (R2 = 0.36, latitude; R2 = 0.30 longitude), supporting the hypothesis that this species recolonized its current northern range following glacial retreat from several refugia in the Washington and Oregon Cascades and in the northern Rockies. Mating system analysis based on simultaneous isozyme analyses of embryo and haploid megagametophyte tissues found relatively high levels of consanguineous mating and selfing for a conifer (tm = 0.73) within populations. Avian seed distribution by the Clark''s nutcracker (Nucifragia columbiana Wilson) appears to be the overriding factor influencing genetic patterns: being a mutualistic seed disperser, caches comprised of related seeds develop into clumped stands with strong family substructure. While it is a critical wildlife habitat component, lack of commercial utilization has made in situ adaptation the primary conservation focus. Encouraging regeneration success and nutcracker caching by maintaining natural fire regimes will provide an ecosystem-based conservation solution; however, in the Rocky Mountains between 52° N and 47° N, disease-resistant individuals should be located and propagated in order to ensure long-term survival of the species in high pathogen hazard areas. [ABSTRACT FROM AUTHOR]

The genetic structure of 19 red alder (Alnus rubra Bong.) populations representing the natural range of the species in British Columbia was investigated at 19 allozyme loci. The estimated average number of alleles per locus (1.79), percentage of polymorphic loci (52.6), and total expected genetic diversity (0.113) were all lower than those reported for most long-lived woody species but comparable to early successional species. About 8% of the total genetic variation was attributable to among-population differentiation, the majority being detected at the Aat-2 locus between the Mainland and the Islands regions. Phylogenetic analysis grouped the 19 populations into two distinct clusters that perfectly coincided with their geographical arrangement. Genetic differentiation between populations within both the Mainland and the Islands regions was very weak, accounting for about 3% of the total genetic variation within each region. Red alder is predominantly an outcrossing species with an average outcrossing rate of 0.85. The rate of outcrossing also varied widely among populations, ranging from 0.56 to 0.98. Practical implications of these findings with respect to tree improvement and in situ gene conservation are discussed. [ABSTRACT FROM AUTHOR]