| Abstract: | ![]()
The Hengduan Mountain Region on the south-eastern fringe of the Qinghai- Xizang (Tibet) Plateau is located in W. Sichuan, N. W. Yunnan and E. Xizang, with a widearea of juxtaposition from the east to the west, the mountains extending and the rivers flowing from the north to the south. In this paper it covers an area from Daojie, Wayao, Yingping,Yangbi, Dali of Yunnan and Dukou of Sichuan in the south, to Banbar, Dengqeu, Shenda of Tibet and Serxu, Dainkog, Shuajingsi and Nanping (Jiuzhaigou) of Sichuan in the north,and from Lharong, Baxoi and Zayü of Tibet in the west, to Maowen, Wenchuan, Mt. Erlang,Mt. Emei and Xichang of Sichuan in the east (Fig. 1.). The Gongga Mountain is the highestin the region, its summit being at an altitude of 7556m, whereas the Dadu River Valley inthe eastern part of the area is only 1150 m above sea level. Therefore, the relative height isabout 6400 m in the region. The Hengduan Mountain Region is well-known for its varioustopography, complex natural conditions and rich flora. The floristic composition and features of orchids in Hengduan MountainRegion. 1. The species of orchids are abundant in the region. As we know so far, orchids in the Hengduan Mountain Region comprise 91 genera and 363 species with 9 varieties, and thusit is one of concentration centres of orchids in China, making up 56.17% of the total numberof orchids genera in China, only less than in Yunnan and Taiwan, and 34.87% of the totalnumber of orchids species in China, only less than in Yunnan and Sichuan. 2. The orchids genera in the Hengduan Mountain Region are complex in geographicalcomponents as indicated below: (1) Four geneva are endemic to China and one of them is endemic to the region. (2) Fourteen genera are of the north temperate distribution pattern, 2 of the Old Worldtemperate one, 18 of the East-Asian one (including Sino-Himalayan and Sino-Japanese) and3 of the East-Asian-North American one. (3) Twenty one genera belong to the tropical Asian distribution pattern, 3 to the tropicalAsian-tropical African one, 13 to the tropical Asian-tropical Australian one, 1 to the tropicalAsian-tropical South American one, 8 to the Old World tropical one and 2 to the pantropicalone. (4) Two genera are cosmopolitan. The analysis of genera: Fourty eight genera (containing 151 species with 4 varieties) of the tropical distribution occur in the region, among which Calanthe and Cymbidiumdistributed in the temperate region, and Bulbophyllum and Peristylus in the subtropical partof China are comparatively abundant (with over 10 species), but the other 25 genera are monospecific and 11 genera each contain only 2-3 species. Some epiphytic genera mainly distributed in tropical Asia and belonging to tropical florestic elements, such as Vanda, Luisia,Schoenorchis, Flickingeria, Monomeria, Kingidium, Acampe, Phalaenopsis, Thrixspermum,Eria, Taeniophyllum, and terrestrial genera, such as Aphyllorchis, Collabium, Mischobulbum,Paphiopedilum, Thunia, Brachycarythis, Satyrium, Corybas, Geodorum, Zeuxine, Tropidia,have the Hengduan Mountain Region as the northern limit of distribution. Of 151 specieswith 4 varieties, 41 species with 4 varieties are endemic to China, and 14 species with 3 varieties of them are endemic to the area, making up 3.86% of the total in the region underdiscussion. There are 41 genera (containing 189 species with 5 varieties) of the temperate distribution,which occur in the region. Among them Platanthera (22 species with 1 variety), Cypripedium (17 species), Herminium (16 species), Amitostigma (15 species with 1 variety), Orchis(12 species), Hemipilia (8 species with 1 variety), Neottianthe (4 species), Gymnadenia (4species), Diphylax (3 species), Bletilla (3 species), have the Hengduan Mountain Region as thedistribution centre and differentiation centre. Among the 189 species with 5 varieties, 111 specieswith 5 varieties are endemic to China, and 54 species with 5 varieties are endemic to the area,making up 14.88% of the total of orchids in the Hengduan Mountain Region. Although thenumber of temperate distribution genera is smaller than that of tropical distribution ones, several points may be mentioned: (1) The Hengduan Mountain Region is distribution centre and differentiation centre ofa number of temperate genera in China, and is the northern limit of many genera mainly distributed in the tropics. (2) The number in the former category is obviously larger than that in the latter. (3) Endemic species in the former category in the area are over three times as many asthose in the latter. The differentiation of species of the temperate distribution genera is obviously strongerthan the tropical ones, which characterizes the orchid flora in the area as the temperate one. The life forms of genera. The orchid flora in the Hengduan Mountain Region so farknown comprises 91 genera, among which 51 are terrestrial, 32 epiphytic and 8 saprophytic,thus with the terrestrial one dominant. The analysis of species: The orchid flora in the Hengduan Mountain Region so far known comprises 363 species with 9 varieties. Their distribution patterns and floristic components, to which they belong, are indicated as follows: (1) Fifty four species, belonging to 33 genera, are widespread, covering the whole East Asian Region, but 6 of them are endemic to China. (2) Forty four species, belonging to 27 genera, are the elements of the Sino-Japanese Subregion, but 22 species of them are endemic to China. (3) One hundred and ninety five species with nine varieties, belonging to 53 genera,are the elements of the Sino-Himalayan Subregion under discussion: (A) Four species (i.e. Aphyllorchis alpine, Listera divaricata, L. pinetorum and Oreorchis micrantha) are distributed in the Himalayan Region and S. E. Xizang (Tibet), westernpart of this region. (B) Twenty five species, belonging to 17 genera, are distributed in N. W. Yunnan andthe Himalayan Region (Appendix, 1.). (C) Sixteen species, belonging to 11 genera, are distributed in the Himalayan regionand W. Sichuan. Among them 6 species occur only with Mt. Emei as the easternmost limit and 10 species occur in the region west of Mt. Emei. (D) Ten species, belonging to 9 genera, are distributed in the Himalayan region, thisregion and S. Shaanxi, S. Gansu or S. E. Qinghai. (E) Eight species, belonging to 6 genera, are distributed in the Himalayan region andthis region. Among them 6 species have their range extending eastwards to Guizhou and 2species eastwards to Guangxi. (F) Five species, belonging to 5 genera, having their range extending from this regionsouthwards to N. Burma. (G) One handred and twenty seven species with nine varieties are endemic to Chinabehind discussion. (4) (A) Three species (i.e. Anoectochilus moulmeinensis, Bulbophyllum forrestii andLiparis chapaensis) are distributed in Indo-China, Burma and the region. (B) Nine species, belonging to 7 genera, are distributed in Indo-China, N. E. Indiaand this region. (C) Forty six species, belonging to 21 genera, are distributed in Indo-China, the Himalayan Region and this region (Appendix, 2.). (D) Twelve species, belonging to 11 genera, are distributed in Indo-China and this region (Appendix, 3.) 3. The vicarism is obvious in the orchid flora of the Hengduan Mountain Region. There are 10 species-pairs (in genera Calanthe, Tropidia, Anoectochilus, Mischobulbum,Bulbophyllum, Gymnadenia, Pogonia, Tipularia, Tulotis, Orchis, etc.) of the horizontal vicarism and 7 species-pairs (in genera Epigeneium, Epipogium, Platanthera, Pogonia, etc.) of thevertical vicarism in the region. 4. The endemic species are prolific in the region. In the orchid flora of the Hengduan Mountain Region there are 155 species and 9 varieties endemic to China: (1) Six species are widespread in the whole East-Asian Region. (2) Twenty two species are the elements of the Sino-Japanese Subregion. (3) One hundred and twenty seven species with nine varieties are the elements of theSino-Himalayan Subregion. Among them 69 species with 5 varieties are endemic to the region (Appendix, 4.), making up 19% of the total in the region; other 58 species with 4 varieties are distributed in the region and neighbouring regions or provinces of it (Appendix, 5.). 5. Remarkable differentiation of the orchid flora in the Hengduan Mountain Region isshown by evident vicarism and abundance of endemic elements, exampled by Amitostigma,Herminium, Orchis, Cypripedium, Platanthera, etc. and one group of Platanthera, which isconfined to the south fringe of the Xizang (Tibet) Plateau-Hengduan Mountain Region. Thegroup consists of 12 species, of which one (P. edgeworthii) is distributed in the Western Himalayas from Hazara in Pakistan to Kumaun in India, and all the other 11 species (i.e.P.stenantha, P. bakeriana, P. roseotincta, P. deflexilabella, P. longiglandula, P. exilliana, P.chiloglossa, P. leptocaulon, P. platantheroides, P. clavigera and P. latilabris) occur in China,with 3 of them (i.e.P. deflexilabella, P. longiglandula and P. chiloglossa) endemic to China.According to their structure of gynostemum and form of labellum they belong to Platantherawithout question, although they are different from the other members of Platanthera in stigmaconvex (not concave) and sepals mammillary-ciliate, stigma exhibits a series of evolutionarytrends in part of species, from stigma single, convex, elliptic and located near rear of spurmouth (in P. stenantha) to stigma single, suddle, and located near front of spur mouth (in P.bakeriana) and to stigma double, separate and located at front of spur mouth in the otherten species. The group in Platanthera is only confined to the area from the south fringe of the Xizang(Tibet) Plateau to the Hengduan Mountain Region. It seems that the genus has been affectedby intense lift of the area, causing variation and differentiation and giving rise to the groupdue to the long-term natural selection. Mt. Emei in Sichuan Province is the eastern limit ofdistribution of the group, where there are three spcies, among which two (P. deflexilabellaand P. longiglandula) are endemic to the mountains. In addition, among Risleya (1 species), Diphylax (3 species) and Diplomeris (2 species),three genera typical of distribution in the Sino-Himalayan Subregion, Risleya and Diphylaxhave Mt. Emei as their eastern limit. Eleven species, belonging to elements of the SinoJapanese Subregion, occur only from Japan to Western Sichuan with Mt. Emei as the westernlimit. Among nine species, belonging to elements of the Sino-Himalayan Subregion, six occurfrom the Himalayas to W. Sichuan and three of them are endemic to the Hengduan MountainRegion, with Mt. Emei as their eastern limit of distribution. There are eight endemic species and one variety of orchids in Mt. Emei, making up about 11.59% of the total endemicspecies in the Hengduan Mountain Region. Orchid floristic elements in Mt. Emei are obviously different from those in Mt. Jinfo, the former being mainly of the Sino-Himalayan Subregion, while the latter being mainly of the Sino-Japanese Subregion. From the distribution patterns of the orchid floristic elements in the Hengduan Mountain Region and EasternChina, the Emei Mountain is considered important for drawing a boundary line between theSino-Japanese Subregion and the Sino-Himalayan Subregion. The discussion may be summarized as follows: the floristic features of the orchid flora inthe Hengduan Mountain Region are: (1) rich in species, complex in geographical components,eminent vicarism and differentiation, and prolific in endemic species; (2) terrestrial life form is dominant one; (3) mainly consisting of temperate and subtropical East-Asian elements, es pecially, elements of Sino-Himalayan Subregion, though with some tropical elements and elem-ents of other regions. |
