Kim, Changkyun, Deng, Tao, Wen, Jun, Nie, Ze Long, and Sun, Hang. 2015. "Systematics, biogeography, and character evolution of Deutzia (Hydrangeaceae) inferred from nuclear and chloroplast DNA sequences." Molecular phylogenetics and evolution, 87 91–104. https://doi.org/10.1016/j.ympev.2015.03.002.
The genus Deutzia (Hydrangeaceae), containing ca. 60 species circumscribed traditionally in three sections, is distributed across East Asia, eastern North America, and Mexico (Central America), with a clear disjunction between Central America and the other regions. Although the genus is well delimited, none of its subdivisions into sections and series have been the subject of an explicit test of monophyly based on molecular data, and a comprehensive examination of the evolutionary relationships within the genus is thus still lacking. We present a fossil-calibrated, molecular phylogeny of Deutzia based on two nuclear ribosomal DNA (ITS and 26S) and three chloroplast DNA regions (matK, rbcL, and trnL-F intergenic spacer). Within this framework, we examine character evolution in petal arrangement, filament shape, and the number of stamens, and infer the ancestral area and biogeographic history of the genus. Our molecular phylogeny suggests that Deutzia is monophyletic. Two major clades are recovered: one composed of the sect. Neodeutzia species from Mexico, and the other containing all remaining Deutzia species of sections Mesodeutzia and Deutzia from SW China, Northeast Asia, and eastern North America, which were revealed to be polyphyletic groups. The induplicate petals, 2-denate filaments, and polystemonous androecia are inferred to be ancestral character states. Biogeographical reconstructions suggest a Northeast Asian origin for the genus and subsequent spread to Mexico during the Oligocene and to SW China and eastern North America during the Miocene. Based on our results, a new infrageneric classification of Deutzia inferred from molecular phylogeny and biogeographic patterns is required. We propose combining the traditional sections Mesodeutzia and Deutzia to conform to the clades. Cooling trends during the Oligocene resulted in isolation, separating East Asian and Mexican taxa, while the warm period during the middle Miocene stimulated the diversification from Northeast Asia to SW China and eastern North America. The uplift in the Qinghai-Tibetan Plateau and monsoon regimes are important in promoting high species diversification of Deutzia in SW China.
