Phylogenetic analyses of Paeonia section Moutan (tree peonies, Paeoniaceae) based on morphological data

Cladistic analysis of the morphological relationship of 40 populations of Paeonia sect. Moutan DC. (including all wild species) was carried out with an attempt to have a better understanding of the phylogerry of tree peonies. Twenty-five morphological characters were selected and used in unweighted pair-group method using arithmetic averages (UPGMA), the neighbor-joining (NJ) and the maximum parsimony (MP) tree construction executed with PAUP* program. The topologies of the trees obtained were largely in congruence and topological differences occurred only between MP tree and the other two in a clade comprising five species, P. suffruticosa, P. jishanensis, P. qiui, P. rockii and P. ostii, which were considered as closely related species based on both morphological and cytological characters. In both NJ and UPGMA trees, all the populations of each species formed a monophyletic clade, and the clades, of P. ludlowii, P. qiui and P. decomposita had strong bootstrap supports ( > 90%), the clades of P. rockii, P. delavayi had moderate bootstrap supports ( > 70%), and the clades of P. suffruticosa, P. ostii and P. jishanensis had weak bootstrap supports (51% - 70%). In MP tree, however, the corresponding bootstrap values of all the clades mentioned above were generally smaller than those in NJ and UPGMA trees and the populations of P. delavayi, P. ostii and P. suffruticosa failed to form monophyletic clades. Based on the above results, interspecific relationships of wild tree peonies were discussed and a phylogeny of sect. Moutan was reconstructed for the first time.