嵩草属地理分布的研究

A STUDY ON THE GEOGRAPHIC DISTRIBUTION OF THE GENUS KOBRESIA WILLD.

嵩草属Kobresia Willd.隶属于莎草科,全世界有64种5变种,中国有49种4变种,属下分为4个组。该属主要分布于北半球温带至寒带,亚洲种类最多,主要集中分布于喜马拉雅山地区和横断山地区。上述两地共有总数的90％以上的种类。因此,喜马拉雅-横断山地区为嵩草属的分布中心。与嵩草属最近缘的属Schoenoxiphium只分布在马达加斯加和非洲东南部山地。两个属可能有共同的祖先,发生于冈瓦纳古陆。随着印度板块与非洲大陆分离并向北方漂移,嵩草属的祖先被带到欧亚大陆,在两个板块相遇处——喜马拉雅-横断山地区产生了现在的嵩草属。其后,喜马拉雅山脉进一步抬升,气候与环境发生巨变,嵩草属也进一步分化形成现在的规模。印度板块在早第三纪与欧亚大陆相连接,嵩草属可能就是此时起源于喜马拉雅山地区,并开始分化,且沿北半球的山系向北扩散到欧洲和西伯利亚,又从欧洲到格陵兰再到加拿大东部,从西伯利亚通过白令海峡到阿拉斯加并沿落基山脉南下达到美国的科罗拉多,形成了嵩草属现今的分布格局。

t The genus Kobresia Willd. , including four sections with 64 species and 5 varieties , belongs to the tribe Cariceae in the family Cyperaceae. The tribe is the most advanced group in Cyperaceae, while the genus is primitive in the tribe. Kobresia is distributed in the temperate to frigid zones of the Northern Hemisphere. All species and varieties, except K. macrocarpa, are found in Asia. They are mainly distributed in the Himalayas and Hengduan Mountains. The genus is especially adapted to frigid habitats, and exists in alpine environments and high latitudes. According to the floristic regionization of Takhtajan (1986) , Kobresia is distributed in four regions of the Holarctic Kingdom and one region of the Pale-otropical Kingdom. (1) The Circumboreal Region- six species, 8. 70% of the total taxa of Kobresia. These species have wide distributions, and two of them, K. bellardii and K. caricina, can be seen almost in the whole range of the genus. (2) The Eastern Asiatic Region; fifty-one taxa, 73. 91% of the total taxa, and twenty-two endemic species. This region is divided into the Sino-Himalayan Forest Subkingdom and Sino-Japanese Forest Sub-kingdom byWu (1979). Forty-one taxa occur in the former, and twelve of them are endemic. Only eight taxa occur in the latter. (3) The Rocky Mountain Region; three species, 4. 35% of the total taxa, and one endemic species. (4) Irano-Turanian Region; thirty-nine species, 56. 52% of the total taxa of Kobresia, and six endemic species. According to the scheme of the Chinese floristic division established .by Wu, thirty-six taxa exist in the Qing-hai-Xizang Plateau Subkingdom, with five endemic. (5) Malesian Region; one species, Ko- bresia. kobresioidea (Kiikenth. ) Kern, which is primitive in the genus and endemic to the northern mountains in Summatra. In Asia, more than 90 % of the total taxa of Kobresia, are found in the Himalayas and Hengduan Mountains. These taxa include the most primitive to the most advanced ones in the genus. The area is not only the center of density, but also the center of diversity of Kobresia, thus it is the center of the distribution of the genus. Kobresia is closely related to the genus Schoenoriphium, which is confined to Madagascar and southeastern Africa. They might have had a common ancestor in the Gondwanaland. With drifting of the India Plate, the ancestor of Kobresia was brought to Eurasia, and differentiated in the Himalayas and Hengduan Mountains where India met Eurasia. The Indian land mass connected Asia in the early Tertiary, and Kobresia probably began to originate in the same time in the Himalayas. The genus reached its greatest speciation with the lifting of the Himalayas, and dispersed along the mountains in the Northern Hemisphere to Europe and Siberia. From Europe, it arrived at Greenland and eastern Canada. From Siberia, it reached Alaska through the Bering strait, and came down along the Rocky Mountains to Colorado.