Cytogeography and taxonomy of the Paeonia obovata polyploid complex (Paeoniaceae)

The taxonomy of the Paeonia obovata polyploid complex in E-Asia has been co ntroversial with treatments ranging from one species and two varieties to f ive species and numerous infraspecific taxa. Extensive observations in the field, analysis of morphological characters based on 32 populations sampled , and the examination of a large amount of herbarium specimens show that al l the characters used by previous authors for distinguishing the species ar e variable between or even within populations: Leaf position, petal colour, stamen number (from 21 to 110 in the red-flowered and from 58 to 239 in th e white-flowered form), filament and anther colour, style length as well as follicle number and position. Therefore, all these characters are of no va lue for species delimitation. However, an extensive chromosome survey and t he analysis of morphological characters show that the ploidy level is basic ally correlated with the geographical distribution and with the indumentum on the lower leaf surface. Thus, the recognition of one species with two su bspecies is proposed: Paeonia obovata subsp. obovata, mostly diploid, widel y distributed in the north, east and south of the distribution range and gl abrous to sparsely pubescent or hirsute on the lower leaf surface, and subs p. willmottiae, tetraploid, limited to the west and with leaves densely hir sute or pubescent below.