Genetic Structure of Hybrid Zones between Pinus pumila and P. pariflora var. pentaphylla.

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Pinus pumila is a creeping shrub which dominates in alpine zone. Pinus parviflora var. pentaphylla is a tall tree in sub-alpine to montane zones. Hybrid zones between the two species are observed mainly in mountains of Tohoku district, Japan. Pinus species exhibit a paternal cpDNA inheritance and a maternal mtDNA inheritance. Previous studies showed that paternal cpDNA flowed from P. parviflora to P. pumila, and in contrast maternal mtDNA from P. pumila to P. parviflora. In addition to diagnostic cpDNA and mtDNA markers, we developed multiple nuclear DNA markers in the present study. We carried out the screening of ESTP primers of Pinus taeda, and finally obtained ten diagnostic marker loci applicable to P. pumila and P. parviflora. Genetic structure of hybrid zones of Mt. Higasiazuma and Mts. Tanigawa were examined by molecular hybrid index. The hybrid index show the percentage of P. pumila marker alleles in the alleles examined. In Higasiazuma, the plants below the sub-alpine conifer forest composed of Abies and Tsuga (1800-1900 m) were genetically similar to P. parviflora, and the average of their hybrid index was 0.073. While, the hybrid index of the plants above the Abies-Tsuga forest were 0.949. This results suggest that the gene flow between the two species are effectively obstructed by the Abies-Tsuga forest. In Tanigawa lacking the sub-alpine conifer forest, hybrid index varied continuously from 0 to 1 according to the altitude of each individuals.We also developed microsatellite markers applicable to P. pumila and P. parviflora. We concentrated DNA fragments having microsatellites by magnetic beads. We determined the nucleotide sequences of about 300 clones, and found 86 unique clones having microsatellites.