Phylogeny and androecial evolution in Schisandraceae, inferred from sequences of nuclear ribosomal DNA its and chloroplast DNA trnL-F regions
Sequences of nuclear ribosomal DNA ITS and chloroplast trnL-F regions were used to construct a phylogeny of Schisandraceae. The results show that there are two major clades in Schisandraceae. One is composed entirely of Schisandra species; the other contains a mixture of Schisandra and Kadsura species. Molecular data place Smith's sect. Sphaerostema of Schisandra prominently within Kadsura, and thus neither Schisandra nor Kadsura is monophyletic, refuting the traditional division of the family into two genera based on morphological characters of mature fruits. The sister relationship between S. glabra ( North America) and S. bicolor ( China) and the monophyly of sect. Sphaerostema and sect. Kadsura are strongly supported. The trnL-F and combined data sets yield phylogenetic trees that are well resolved and concordant with androecial types of staminate flowers; however, they do not support the evolutionary pathways for androecia constructed by previous authors for Kadsura and Schisandra. The new alignment of species in Schisandraceae indicates that morphological characters traditionally used to construct phylogenetic relationships and evolutionary pathways, e. g., habit ( deciduous vs. evergreen or semievergreen), fruit type (bacceta vs. separated apocarps), arrangement of flowers ( solitary vs. paired or in glomerules), and pollen (3-colpate vs. 6-colpate), evolved more than once in the family. Preliminary observations suggest that the pentagonal androecium and gynoecium of S. glabra are thermogenic and that heat may play a role in the reproductive biology of S. glabra to enhance floral odor or simulate the temperature of brood sites for many types of insects.