Tribe Neillieae, characterized within Rosaceae by stipulated simple leaves, ovoid seeds, and copious endosperm, comprises three taxonomically difficult genera, Neillia, Stephanandra, and Physocarpus. As part of a comprehensive systematic study of the tribe, nucleotide sequences of the ITS and 3 partial ETS regions of nrDNA, trnL-trnF and trnD-trnT regions of cpDNA, and the second intron of a floral homeotic gene, LEAFY, were determined to elucidate phylogenetic relationships in the tribe Neillieae. The maximum parsimony analyses of nrDNA and cpDNA data set indicate that two major clades (Physocarpus and Neillia/Stephanandra) are strongly supported in tribe Neillieae, but the relationship between Neillia and Stephanandra is inconsistent. The level of sequence divergence of the second intron of LEAFY is about 5-fold higher than that of nrDNA and the intron sequences are phylogenetically useful. Separate phylogenetic analyses of three data sets (nrDNA, cpDNA, and LEAFY) suggest that the P. opulifolius complex may have been originated by a hybridization between P. monogynus and P. capitatus. The results also suggest that Stephanandra may be of hybrid origin.

Key words: cpDNA, LEAFY, Neillieae, nrDNA, Phlogeny, Rosaceae