T. Qian et al., GENETIC-RELATIONSHIPS AMONG LARCH SPECIES BASED ON ANALYSIS OF RESTRICTION FRAGMENT VARIATION FOR CHLOROPLAST DNA, Canadian journal of forest research, 25(7), 1995, pp. 1197-1202
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.