Variation And Evolution In Paeonia Sect. Paeonia (Paeoniaceae): Evidence From Morphology, Chromosome And Gene Sequences

The genus Paeonia, comprising ca. 35 species of shrubs and perennial herbs, is disjunctively distributed in the northern temperate regions. Three sections, Moutan, Onaepia, and Paeonia, have been recognized within the genus. The section Paeonia consists of ca. 25 herbaceous species, of which half are tetraploids (2n=20). These tetraploid species are mostly distributed in the Mediterranean region. Although some evidence supported the section Paeonia to have undergone complicated reticulate evolution, there is still event that suggests reticulate origins of some species within the section. In this study, the reticulate evolutionary history of sect. Paeonia was explored by using eight DNA sequences of chloroplast (matK, trnL-trnF, psbA-trnH, and rps16-trnQ) and nuclear genomes (Adh1, Adh2, ITS, GPAT). In addition, the phenotypic, karyotypic as well as cytogenetic features were also studied in understanding the origin of P. anomala, a species distributed in Xinjiang, China, and geographically mediated the Asiatic and Mediterranean groups. The main results are summarized as follows:1. Phylogenetic reconstruction of sect. PaeoniaAlmost all diploids and tetraploids of sect. Paeonia were sampled to reconstruct the evolutionary history of the section based on five DNA fragments from chloroplast (matK, rps16-trnQ) and nuclear genomes (Adh1, Adh2, ITS). The separate and combined analyses on these sequences by maximum parsimony, Bayesian MCMC and maximum likelihood methods indicated that:(a) The diploid species except P. tenuifolia,distributed in the Mediterranean region, were structured into a monophyletic group, which consists of a paraphyletic relationship with P. tenuifolia and Asian diploids.(b) The inconsistency of phylogenies reconstructed by cpDNA and nrDNA, plus the ITS and Adh polymorphisms, suggested there were interspecific hybridization events at either diploid and tetraploid levels. An individual, XJ053, is such an interspecific hybrid between P. anomala and P. intermedia, distributed in Altai,...