Fig. 6. Phylogeny of Paeonia section Paeonia reconstructed from a synthesis of the ITS and matK

phylogenies. Solid lines represent divergent and patristic evolution, but length of lines is not proportional to amount of patristic change. Dashed lines represent reticulate evolution. Solid circles, maternal parents; open circles, paternal parents; shaded circles, parents with uncertain maternity or paternity; shaded squares, hybrids; open square, a hybrid with fixed ITS sequences similar to its paternal parent; open ellipse, hybrid species with fixed paternal ITS sequences; shaded ellipse, hybrid species with fully additive ITS sequences from their parents; striped ellipse, hybrid species with partially additive ITS sequences from their parents. An attempt is made to indicate the relative order of occurrence of hybridizations, but it may not be totally accurate. Hybrid species completely fixed for one parental type ITS sequence or with partially additive ITS sequences are considered to have a more ancient origin than species with full ITS additivity if we assume that gene conversion operated at a relatively constant rate over all hybrids. Hybrid species identified by ITS additivity but without maternal parents identified by matK sequences are considered to have a more ancient origin than those sharing matK mutations with their maternal parents if we assume that lack of shared matK mutations is due to occurrence of hybridization prior to accumulation of mutations in the maternal parents. Species abbrevations as in Fig. 1. d= diploid; t= tetraploid; b= both diploid and tetraploid populations known; u= ploidy level unknown.