论无心菜属的地理分布

ON THE GEOGRAPHICAL DISTRIBUTION OF ARENARIA L.

全世界无心菜属植物有306种,隶属10亚属24组,主要分布于欧、亚、美三洲和北非,基本上是北温带分布属。文章分析了亚属的系统位置及其分布式样。地中海区到西亚亚区和中亚亚区的西北部是其分布区中心,也可能是它的起源地,中国横断山脉到青藏高原是其次生分布中心。起源时间至少应该追溯到白垩纪中期。最后,讨论了它的散布途径和现代分布式样的形成及其原因。

The present paper aims to discuss the geographical distribution of the Arenaria L. on the basis of the unity of phylogeny and process of dispersal in plants. There are 306 species of Arenaria in the world, belonging to 10 subgenera and 24 sections. Arenaria are mainly distributed in Eurasia, America and northern Africa. According to the geographical elements of Arenaria in the world, eight geographical distribution pattern and 11 variants are divided. According to Takhtajan' s and Wu' s view points of phytochoria, the number of species is counted for each region, which shows clearly that the Mediterranean, W. Asia to northwest C. Asia region and Hengduan Mountains to Qinghai-Xizang(Tibet) Plateau region of China have greatest numbers of subgenera and species. There are six subgenera and 105 species in China, and especially its southwest part, Xizang ( Tibet) , Yunnan and Sichuan, is richest in subgenera and species. According to Lu' s view point of centre of floristic region, it is determined by the following two principles; (a) A large number of species concentrate in a district, namely the centre of frequency; (b) species of a district can reflect the main stages of the systematic evolution of Arenaria, namely the centre of diversity. It is clear that the Mediterranean, W. Asia to nothwest C. Asia region form the main distribution centre of A renaria, while the Hengduan Mountains to Qinghai-Xizang (Tibet) Plateau Region form the secondary distribution centre. On the basis of separation time of the South American continent from the African continent, the origin of Arenaria might date back to the Middle Cretaceaus. After the emergence of Arenaeia plant on the earth, it first developed and dispered in northern Mediterranean. During the period of its origin and development , Arenaria rapidly developed and dispered to North Africa, Cental America to South America and from Eurasia to North America by three routes; the Mediterranean-North Africa-Central America-South America route, Europe-Greenland-North America route and Asia-Bering Bridge-North America route. Finally, the formation of the modern distribution pattern and the factors involved in this formation are discussed. The probable evolutionary relationships of the subgenera of Arenaria are inferred in the text.