| Abstract: | The genus Cyananthus is distributed in the Himalayan Floristic Subregion. Inthe early years, it was treated as a member of Polemoniaceae, but it is now generally regardedas a natural group of Campanulaceae. Made in this paper were a comprehensive comparativemorphological study, a biometrical analysis of quantitative characters and an analysis of distribution pattern. The systematic position of the genus is discussed based on the evidence from pollen morphology, chromosome number and external morphology. Finally the classification ofthe genus is revised.As a result of the character analysis, the evolutionary trends of the characters in Campanulaceae are suggested: superior ovary is a primitive state; the pollen grains have evolvedfrom long-multicolpal to short-colpal, then to multiporate; the basic chromosome numbershave changed from 7 to 8 or 9, from which the groups with x=17 are derived (see Fig. 2),Fig. 2 illustrates that Cyananthus is the most primitive genus in the Gampanulaceae, closelyrelated to Codonopsis, Platycodon, Leptocodon and Campanumoea. All these genera are relatively primitive in the family.The genus Cyananthus is distributed in S. E. Gansu (Zhugqu), W. Sichuan, S. and E.Xizang, S. Qinghai and N. W. Yunnan, extending westwards to Kashmir along the Himalayas. Therefore, the genus is strictly limited to the Hengduan Mountains and the Himalayas.That is to say, it occupies the whole Sino-Himalayan Floristic Subregion (Fig. 3). This is ofgreat importance for determining the limits of the floristic subregion, and for drawing a moreacurate line between the Sino-Japanese Subregion and the Sine-Himalayan Floristic Subregion.The analysis of distribution patterns of species shows that the Hengduan Mountains is the distribution centre of the two major groups of Cyananthus, Sect. Stenolobi Franch. and Sect.Annui (Lian) Hong et L. M. Ma. In these two groups, only four out of 12 species, i. e. C. incanus Hook. f. et Thoms., C. macrocalyx Franch., C. hookeri C. B. Cl. and C. inflatus Hook. f. et Thoms., extend their areas westwards to Sikkim and Nepal. The other section, Sect.Cyananthus also exists in the west of the Hengduan Mountains. Although in the Himalayas occur three major groups of the genus, only the last-mentioned group-Sect. Cyananthusis mainly distributed in the area (Fig. 4). According to the fact, we tend to infer that the Hengduan Mountains is both the frequency and diversity centers of the genus Cyananthus. The generaof Campanulaceae, which are relatively primitive and the closest relatives of Cyananthus, all occur in SW China and the adjacent regions. Therefore, the region may well be the preserved center of the primitive genera, or even may be the original center of the Campanulaceae.All data accumulated demonstrate that the genus is very old but still under intensive differentiation. With few diagnostic qualitative characters, the characters used in classifications aremostly quantitative ones. The following characters were usually used for classification of thegenus: habit, plant size, leaf shape, leaf size, hairs on the leaf, corolla colour, petiole length, corolla length and hairs on the calyx, etc. Among them, only habit, corolla colour and hairs belong to qualitative characters, and all of the others are quantitative ones. Because variation ranges of quantitative characters have never been thoroughly studied in the previous classifications,some named taxa are artificial. An extensive statistical analysis of quantitative characters werecarried out in the work to reveal their variation ranges. Based on this, 5 specific names are reduced as synonyms: C. microrhombeus C. Y. Wu is reduced to C. delavayi Franch.; C. argenteusMarq. to C. longiflorus Franch.; C. pseudo-inflatus Tsoong to C. inflatus Hook. f. et Thoms.;and both C. neurocalyx C. Y. Wu and C. leiocalyx (Franch.) Cowan to C. macrocalyx Franch., while C. montanus C. Y. Wu and C. Petiolatus Franch. are treated as subspecies in C. flavus Marq. and C. incanus Hook. f. et Thoms. respectively. As a result of the revision, 19 species and 2 subspecies are recognized in the present paper, with 7 species names and 15 varietynames reduced.The genus is divided into three sections according to habit, corolla lobes and hairy typeson calyx: Sect. Cyananthus, Sect. Stenolobi Franch. and Sect. Annui (Lian) Hong et L. M.Ma.In the present paper the chromosome number of the genus Cyananthus is reported for thefirst time, C. inflatus Hook. f. et Thoms. from Yadong, S. Tibet, being found to have 2n=14.And pollen morphology of the genus Leptocodon was first examined under SEM and is shownin Plate 1. |
