The Systematics Of Tulipa L. (S. L.) From China

Tulipa L. is an element of the tribe Tulipeae in the Liliaceae (s. s.), and has been popular as ornamental plants because of their large and showy flowers. Its distribution area ranges from Europe, the temperate regions of Asia to NW Africa. This genus is composed of 40-150 species in seven sections, i.e. sect. Amana, sect. Tulipanum, sect. Leiostemones, sect. Spiranthera, sect. Lophophyllon, sect. Eriostemones and sect. Orithyia. Sect. Amana is confined to E. Asia. There are 16 species of this genus distributed in China, among which four species belong to sect. Amana. Because of the lack of adequate knowledge of biological characteristics and geographic distribution on sect. Amana, it has long been in dispute if this taxon should be included in the genus Tulipa L. or treated as an independent genus of its own. The present thesis is to report the results of works on the analysis of morphology, embryo sac development and molecular systematics of Tulipa L. (s. l.) from China, and attempts to evaluate the significance of the above features in taxonomy, The restoration of Amana Honda as a genus is also made based on the result of this comprehensive study. The main points are as follows: 1) Based on both herbarium and field observations on the Chinese taxa of Tulipa L. (s. l.), particularly those in sect. Amana, a cladistic analysis of 18 species (including three from Turkey) of Tulipa L. was carried out. Twenty-eight morphological characters were used in unweighted pair-group method using the maximum parsimony (MP) tree construction executed with PAUP 4.0b4a program. The results show that Tulipa L. (s. l.) is not a monophyletic group but splits into two clades: one is sect. Amana, and the other comprises sect. Orithyia, sect. Eriostemones, sect. Leiostemones and sect. Tulipanum. The section Amana differs from Tulipa L. (s. s.) in having 2-3 (-4) opposite or verticillate bracts and a longer style as long as the ovary. The sect. Amana is thus better treated as an independent genus. 2) Amana kuocangshanica D.Y. Tan et D. Y. Hong is described as new from Mt. Kuocang, Zhejiang Province in SE. China. Morphological observations on the new species and its relatives and statistical analysis based on population sampling show that it is most closely related to A. anhuiensis and A. erythronioides, but differs from them in having the lower leaf lanceolate, the widest at 2/3 length from the base, tunics glabrous inside, and fruit beak 0.64 ± 0.08 cm long. 3) The morphological characteristics of leaf epidermis of 16 species were studied. The results show that in the four species of Amana Honda, the epidermal cells are rectangular, narrow oblong or rhombic, with the anticlinal wall straight or sinuous on both surface, where stomatal apparatus are sparse or even absent. These characteristics are obviously different from those in Tulipa L. (s. s.). In Tulipa L. (s. s.), obvious differences in morphology of leaf epidermis exist between species, but not between sections. These results indicate that the characteristics of leaf epidermis have some value in taxonomy and studies on relationships between species in Tulipa L. (s. l.). 4) The pollen morphology of 19 species in Tulipa L. (s. l.) was investigated under SEM. The results show that there are five types of exine ornamentations in Tulipa L. (s. l.), i.e. reticulate, striate-reticulate, tuberculate, verrucate and rugose-sinuate. Pollen grains of all the four species in Amana Honda is elliptic, scaphoid or reniform with reticulate exine ornamentations. These characteristics are obviously different from those in 15 species of Tulipa L. (s. s.). In Tulipa L. (s. s.), there are obvious interspecific differences in pollen exine ornamentations, and these features can be used as one of characters in taxonomic treatment of species, but have no value for the division of sections in Tulipa L. (s. s.). 5) Observed were the morphological features of seeds in 16 species of Tulipa L. (s. l.). The surface structure of seeds can be divided into three types: reticulate, areolate and rugose-sinuate. In Amana Honda, seeds are small, semilunar, with a thick seed-coat and an obvious stipe, but with embryo unvisible. Surface cells of seeds are of undulate anticlinal wall and irregular in shape. These characteristics are different from those of Tulipa (s. s.). In 12 species of Tulipa L. (s.s.), there are obvious interspecific differences in ornamentations of seed-coat, size and shape and width ofraphe. The morphological features of seed-coat are useful for taxonomy in Tulipa L. (s. s.). 6) There are six types of embryo sac development in 16 species of Tulipa L. (s. l.) from China: Eriostemones type, Fritillaria type, Adoxa type, Drusa type, Tulipa illiensis type and Tulipa tetraphylla type. Among them, Tulipa illiensis type is a new type of embryo sac development discovered in Tulipa iliensis. There are two types of embryo sac development in T. iliensis, T. heterophylla and T. heteropetala. The types of embryo sac development may be of some significance in systematics of Tulipa L. (s. s.). 7) The phylogenetic analyses of 21 species of Tulipa L. (s. l.) and two species of Erythronium L. using nrDNA ITS and cpDNA trnL-trnF region sequences, do not support the monophyly of Tulipa L. (s. l.). Amana and Erythronium form a monophyletic group sister to with Tulipa L. (s. s.) in the ITS phylogeny and combined analysis of the two DNA regions, supporting the separation of Amana from Tulipa L. (s. l.). However, Amana + Erythronium clade was nested within Tulipa L. (s. s.) in the trnL-trnF phylogeny. In Tulipa L. (s. s.), sect. Orithyia, sect. Eriostemones and sect. Tulipanum are monophyletic, but sect. Leiostemones is paraphyletic in some analyses, and its systematic position needs to be further clarified.