GENETIC-RELATIONSHIPS AMONG LARCH SPECIES BASED ON ANALYSIS OF RESTRICTION FRAGMENT VARIATION FOR CHLOROPLAST DNA

The genetic relationships among eight species and three varieties with in the genus Larix were studied by analysing restriction fragment leng th polymorphism in chloroplast DNA (cpDNA). Six restriction enzymes an d 11 predominantly nonoverlapping probes from Pinus contorta Dougl. ex Loud. were employed. No variation in cpDNA was detected within taxa, and mean levels of nucleotide divergence ((d) over cap) among species were low. Six taxa were not resolved by the analysis, and the maximum d value recorded was 0.0096. Genetic distance data and neighbor joinin g were used to construct a tree of genetic relatedness among taxa, whi ch resolved three groups. Larix griffithiana Can. was genetically dist inct from all other taxa. A second group comprised Larix sibirica Lede b. from Eurasia and two North American species, Larix laricina (Du Roi l K Koch. and Larix occidentalis (Nutt.). The third group consisted of the Chinese and Japanese taxa Larix gmelinii (Rupr.) Rupr. ex Kuzen., Larix potaninii Batal., and Larix kaempferi (Lamb.) Can. together wit h European larch, Larix decidua Mill.. These groupings do not correspo nd to traditional patterns of classification within the genus, which a re based primarily on features of the female cone. The results from th e cpDNA analysis are interpreted in the context of other information a bout the evolutionary history of the genus.