Molecular systematical Studies of Cupressaceae and Taxodiaceae using DNA sequence information

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The molecular evolution of two families, Cupressaceae and Taxodiaceae, was elucidated using DNA sequence information on four chloroplast DNA genes, atpA, petA, rbcL, and rpo3. The principal results are as follows :(1) The molecular phylogeny of families Cupressaceae and Taxodiaceae revealed that they consisted of five clades and that family Cupressaceae was comprised within family Taxodiaceae.(2) In petA gene, the sequence polymorphism was recognized between Chamaecyparis obtusa and C.obtusa var. formosana. Using this information, the two species came to be identified correctly.(3) In the phylogeny of the genus Chamaecyparis, Alaska cypress (Chamaecyparis nootkatensis) was distant-related from the remaining six species/variety phylogenetically. This genus was divided into three clades.(4) The hybridity of Leyland cypress (x Cupressocyparis leylandii) was verified based on DNA information. We found the molecular evidence that the nucleic genome of Leyland cypress originated from Monterey cypress (Cupressus macrocarpa) and Alaska cypress in the Cupressaceae and that this species is of hybrid origin.(5) Systematical position of Alaska cypress was predicted in the genus Chamaecyparis. A new finding that this species should be classified as a member of the genus Cupressus was revealed based on molecular phylogenetic trees.(6) The family Cupressaceae was divided into two monophylic clades distributed in the northern hemisphere and the southern hemisphere. The genera of the southern hemisphere diverged at first. The genera Thujopsis and Thuja secondary separated, and the genera Cupresus and Juniperus were newly formed.(7) The genus Callitris was the latest-diverged in family Cupressaceae and the species of this genus was radiated in a relatively short term.