LI, JIANHUA1,2,3*, PETER DEL TREDICI1, SHIXIONG YANG4, and MICHAEL J. DONOGHUE5. 1Arnold Arboretum of Harvard University, 125 Arborway, Jamaica Plain, MA 02130; 2Department of Plant Biology, University of New Hampshire, Durham, NH 03824; 3University of Maine, Orono, ME 04469; 4Institute of Botany, Academia Sinica, Kunming, Yunnan 650204, China; 5Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06511. - Phylogenetic relationships and biogeography of Stewartia (Camellioideae, Theaceae) inferred from nuclear ribosomal DNA ITS sequences.
Sequences of the internal transcribed spacers of nuclear ribosomal DNA
were used to estimate phylogenetic relationships within
Stewartia. Eighteen samples were included, representing two
species of Hartia, seven species of Stewartia, and an
outgroup, Franklinia alatamaha. Several different inference
methods were used, including parsimony, neighbor-joining, and maximum
likelihood. Parsimony analyses were conducted treating gaps as missing
data or as a fifth character state. In all analyses Hartia
sinensis and H. villosa form a clade that is the sister
group of Stewartia. Within Stewartia the New World and
the Old World species form well supported clades. The subgenera and
sections of Stewartia proposed by previous authors are not
supported by our ITS data. Two clades are recognized within the Old
World lineage: S. serrata+S. rostrata; and S.
pseudocamellia+S. monadelpha+S. sinensis. A
comparison of levels of sequence divergence suggests that southeast
Asia and China may be a recent center of diversification in
Stewartia. Morphological disparity between the North American
Stewartia species is much higher than it is among the larger
number of Asian species.
Key words: biogeography, Hartia, morphological disparity, nrDNA ITS, phylogeny, Stwartia, Theaceae