| his study investigates evolutionary and distributional histories of Paeonia (Paeoniaceae), a flowering plant genus containing approximately 35 species occurring in several disjunct areas in the northern hemisphere. DNA sequences, including sequences of internal transcribed spacers (ITS) of nuclear ribosomal DNA (nrDNA), the matK coding region of chloroplast DNA (cpDNA), and cpDNA intergenic spacers of psbA-trnH and trnL(UAA)-trnF(GAA), were obtained as sources of evidence for phylogenetic reconstructions.;Reconstruction of complex reticulate evolution (speciation via hybridization) in Paeonia section Paeonia is the most significant contribution of this study. A number of hybridization events were revealed based on nucleotide additivity detected by directly sequencing PCR products of the ITS region. The partial and uneven homogenization of parental ITS sequences displayed in nine species of hybrid origin was suggested to be results of gradients of gene conversion. In addition to the hybrid species detected by ITS sequence additivity, those ones that have fixed the paternal type of ITS sequences are identified by comparing their different positions on the ITS and matK phylogenies. This study demonstrates that nuclear DNA sequence data can be highly informative and accurate for detecting hybridization, and comparison of nuclear and cpDNA gene phylogenies may represent an effective way to reconstruct reticulate evolution in plants.;Based on molecular evolutionary studies, classification, evolution of morphology and cytology, and biogeography of Paeonia are discussed. Among species of hybrid origin in section... |
