Molecular phylogeny of Nothofagus (Nothofagaceae) based on the atpB-rbcL intergenic spacer of the chloroplast DNA
1997
Setoguchi, H. (Tokyo Metropolitan Univ., Hachioji (Japan). Faculty of Science) | Ono, M. | Doi, Y. | Koyama, H. | Tsuda, M.
The genus Nothofagus is distributed in the Southern Hemisphere from South America to Oceania, and its distribution has been assumed to be formed by continental drift by means of Gondwana break-up during the Mesozoic era. The phylogeny of the genus was elucidated by the sequences of atpB-rbcL intergenic spacer of cpDNA for the butter understanding of its evolution and biogeography. The phylogeny of Nothofagus corresponded completely to the pollen morphology which recognizes four pollen types in extant species, and agrees well with the taxonomic system of Hill and Read (1991) although there, the subgenus Nothofagus showed in unresolved polytomy. The topology of the phylogenetic tree reveals that subgenus Lophozonia was derived first, and then Fuscospora, Nothofagus and Brassospora. Species from South America and New Zealand were assigned to each cluster according to their pollen morphology. Therefore, diversification of Nothofagus should have already proceeded at the subgenus level before the completion of Gondwana break-up. Tropical species distributed in New Guinea and New Caledonia whose evolutionary history has been controversial were revealed to be a derived group. All five New Caledonia species formed a monophyletic group with very few sequence divergences in the intergenic spacer of cpDNA, thus showing rapid adaptive radiation in the island. Evolutionary trends of several morphological traits of Nothofagus are discussed. The evolution of valve number of cupules, number of nuts per cupule, and habit of leaf-fall (evergreen or deciduous) which are diversified in the genus, were revealed as having occurred several times as the result of convergence
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