Geographic patterns of genetic variation and population structure inPinus aristata, Rocky Mountain bristlecone pine

Abstract

Pinus aristata Engelm., Rocky Mountain bristlecone pine, has a narrow core geographic and elevational distribution, occurs in disjunct populations, and is threatened by 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 (He = 0.070 and 0.062, respectively) occurred with moderate among-population differentiation (FST = 0.131). Genetic diversity correlated with longitude, latitude, and elevation and a strong mountain island effect may contribute to substructuring and isolation. Using multiple complementary analyses, sampled trees were assigned to three genetic lineages that varied in diversity and admixture and were associated with different climatic factors. The distribution of genetic diversity and substructuring of P. aristata may be an outcome of a combination of restricted gene flow due to geographic and phenological isolation, random processes of genetic drift, life history traits, natural selection, and postglacial migrations. The combination of low genetic diversity, moderate population isolation, and a protracted regeneration dynamic puts populations at risk for extirpation by novel stresses.Résumé : Pinus aristata Engelm., le pin aristé, possède une distribution centrale restreinte, tant géographique qu'altitudinale. L'espèce se retrouve en populations isolées et est menacée par la rapidité des changements climatiques, la rouille vési-culeuse du pin blanc et les scolytes. La connaissance de la diversité génétique et de la structure de populations aidera à orienter les stratégies de conservation des ressources génétiques chez cette espèce. Les auteurs ont échantillonné 16 populations réparties dans les quatre chaînes de montagnes se retrouvant au coeur de la distribution centrale de P. aristata. La diversité génétique a été évaluée pour 21 loci d'isoenzymes. Une diversité génétique faible fut remarquée, tant pour l'espèce que dans les populations (He = 0,070 et 0,062, respectivement). La différenciation de populations était modérée (FST = 0,131). La diversité génétique était corrélée avec la longitude, la latitude et l'altitude, et un fort effet insulaire dû aux montagnes pourrait contribuer à la sous-structuration et à l'isolement. En recourant à des analyses multiples complémentaires, les arbres échantillonnés pouvaient être assignés à trois lignées génétiques qui variaient quant à leur diversité et leur composition et qui étaient associées à différents facteurs climatiques. La distribution de la diversité génétique et la sous-structuration de P. aristata pourraient être la résultante d'une combinaison de facteurs incluant le flux génique restreint en raison de l'isolement géographique ou phénologique, les processus aléatoires découlant de la dérive génétique, les caractéris...

Evaluation of RAPD markers for molecular identification of five bamboo genera from Indonesia

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