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Title: Geographic patterns of genetic variation and population structure in Pinus aristata, Rocky Mountain bristlecone pine

item SCHOETTLE, ANNA - Us Forest Service (FS)
item GOODRICH, BETSY - Us Forest Service (FS)
item HIPKINS, VALERIE - Us Forest Service (FS)
item Richards, Christopher
item KRAY, JULIE - Us Forest Service (FS)

Submitted to: Canadian Journal of Forestry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/12/2011
Publication Date: N/A
Citation: N/A

Interpretive Summary: The Rocky Mountain Bristlecone pine (Pinus aristata) has a narrow core geographic distribution compared to other five-needle pines in the Rocky Mountains and occurs in local and fragmented sites. This species is one of the longest living plants in the world and serves as a critical ecological role in high altitude habitats. The species is currently threatened by climate change, an invasive pathogen (white pine blister rust) and native bark beetles. Little is currently known about the species genetic structure. This study analyzes molecular diversity data and estimates three main genetic lineages within the species range. Understanding the genetic diversity and population structure in the core of the species’ range will help target collection of seeds to particular sites for long term storage in genebanks as part of a comprehensive conservation management strategy for this species.

Technical Abstract: Pinus aristata Engelm., Rocky Mountain bristlecone pine, has a narrow core geographic and elevational distribution, occurs in disjunct populations and is threatened by multiple stresses, including rapid climate change, white pine blister rust, and bark beetles. Knowledge of genetic diversity and population structure will help guide gene conservation strategies for this species. Sixteen sites across four mountain ranges in the core distribution of P. aristata were sampled and genetic diversity was assessed with 21 isozyme loci. Low species and population level genetic diversity (expected heterozygosity [He] = 0.070 and 0.062, respectively) occurred with moderate among-population differentiation (FST = 0.131). Populations were more highly differentiated than mountain ranges, though both were significant, and the north-central zone of the distribution is an area of apparent historical gene flow. Genetic diversity correlated with latitude, longitude and elevation, and a strong mountain island effect may contribute to sub-structuring and isolation. Sampled trees assigned to three genetic lineages that varied in diversity and admixture and were associated with different climatic factors. The combination of low genetic diversity moderate population isolation and a very protracted regeneration dynamic for P. aristata put populations at risk for extirpation by novel stresses. The multiple complimentary analyses presented here reveal a pattern of genetic variation relevant to management. We recommend that gene conservation strategies for P. aristata include sampling the full range with more intensive sampling focused in areas with higher genetic diversity, allelic richness and private alleles. Immediate collections will capture the genetic diversity before erosion by novel stresses.