Taxonomic revision of Syringa pinetorum complex (Oleaceae)

Five species of the Syringa pinetorum complex described by previous authors are revised. Syringa wardii W. W. Sm., S. mairei (H. Lev.) Rehder, S. rugulosa McKelvey and S. chuanxiensis S. Z. Qu & X. L. Chen are treated as synonyms of S. pinetorum on the basis of population sampling, character analysis and principal coordinate analysis, and S. mairei is a new synonym. Only one variable species, S. pinetorum, is here recognized in the complex. were sampled across northern Yunnan and western Sichuan according to the type localities. About one hundred herbarium specimens from Sichuan, Yunnan and Xizang were examined. The specimens from the Lancangjiang Valley represent the population DI, those from Xizang region represent the population XZ, and the others were incorporated into the previous five populations. Therefore, a total of seven popula- tions were used in the analysis. Size and shape of leaf blades were often used to distinguish S. wardii from S. pinetorum. Smith (1916) described the former by its leaf blades suborbicular, 1-2 cm long and broad (vs. ovate, 2-3.5×1-1.6 cm in the latter). Green and Chang (1995) described S. pinetorum having leaf blades 1.5-3×0.6-1.8 cm; S. wardii, 1.2-2.2×1.2-2.2 cm; and S. mairei, (2-)4-4.5(-6)×(1.5-)2-2.5(-3) cm. Our observation and analysis show that length, width and the ratio of length to width of leaf blades vary continuously