Wen-Jing YANG, Liang-Qian LI, Lei XIE
2009, 47 (6): 552–580
Clematis sect. Atragene is revised in this paper based on the examination of a large number of herbarium specimens, the extensive field observations, and the morphometric analyses. Brief taxonomic history and geographical distribution of the section are given, the relationships among the species are discussed, and the evolutionary trends of some characters in the section are evaluated. The staminodes of the plants in this section may have evolved from the outer stamens with petaloid filaments and gradually disappearing anthers. Subsequently, they may have evolved in two different ways. One is that the staminodes elongate and become lanceolate, as long as sepals, and their apices turn into attenuate. The other is that the staminodes are spathulate, but not elongating, as long as stamens, and their apices turn into retuse from obtuse and rounded. The evolutionary trend of sepals perhaps is from thin to thick in texture, and the veins are from non-prominent to prominent. As a result, five new series are established and nine species, two subspecies and nine varieties (including three new ranks) are recognized in this section. An identification key is provided, and each taxon is described and illustrated. Clematis sibirica and C. ochotensis are treated as subspecies of C. alpina due to their subtle differences and none or little overlapping distributions. Clematis fusijamana and C. fauriei are recognized as varieties of C. alpina ssp. ochotensis for the continuous variation of the velutinous strips on the sepal margins. Clematis iliensis is treated as variety of C. alpina ssp. sibirica for the continuous variation of leaf division types. Extensive variations in sepal colour and basal caruncle size support degrading C. chiisanensis as a variety of C. koreana. The North American ser. Occientales may be primitive, whereas ser. Macropetalae may be the most advanced taxon in this section. Ser. Alpinae and ser. Koreanae are closely related to each other. However, the systematic position of ser. Tomentosae cannot be determined based on morphological characters alone in the present study.