鹅观草属的地理分布

Geographical distribution of Roegneria C. Koch (Poaceae)

鹅观草属是禾本科小麦族中的最大的属 ,现知全世界有 4组、2 0系、1 2 6种 ,分布于北半球的温带和寒带 ;中国有 4组、1 8系、79种 ,主要分布于西北、西南、华北和东北 ,是鹅观草属植物种类最为集中的区域 ;尤其青藏高原东北部的唐古特地区又是我国鹅观草属分布相对密集之地 ,有 3组、1 2系、30种 ,而且其间不同等级、不同演化水平的类群均有分布 ,该地可能就是该属的现代分布中心。同时 ,唐古特地区多汇聚有鹅观草属不同等级的原始类群和与原始类群很近缘的短柄草属植物 ,其中最原始的大柄鹅观草特产于该区 ,而该区缺乏的是高级的大颖组类群 ,故推测唐古特地区可能又是该属的起源地 ,起源时间大约在青藏高原明显增高、气候转凉的晚第三纪初的中新世。鹅观草属起源后 ,在中国境内地质活动比较剧烈的地区得到了进一步的发展和分化 ,但只有少数适应性较强的类群大概以 3条路径扩展到国外 ,并向东到达北美的巴芬岛 ,向西延伸到大西洋滨岸 。

Roegneria is the largest genus in Triticeae of Poaceae,including 126 species,20 series and 4 sections.The genus is only distributed in the temperate and frigid zones of the Northern Hemisphere.According to Takhtajans (1978) regionalization of the world flora, Roegneria was found in 7 regions.Irano-Turanian region with 105 species,of which 70 are local endemics,20 series and 4 sections,ranks the first among all the regions.The highest concentration of the taxa and endemics in the region occure in China.The chinese taxa of Roegneria include 79 species,18 series and 4 sections,and are mainly distributed in Northwest,Southwest,North China and Northeast regions of the country.The most abundant area for section,series and species is in the Tangut region regionalized by C.Y.Wu in 1979.In this small area there are 30 species,13 series and 3 sections,and these taxa include the primitive to the most advanced ones in the genus.These facts indicate that NE Qinghai Xizang Plateau is probably the distribution center of Roegneria .Furthermore,the Tangut region has a lot of primitive taxa of Roegneria ,of which R.magnipoda is the most primitive species in the genus,also a endemic species in the region.In Tangut region,on the contrary,there is not the sect. Ciliaria which is considered as the most advanced section in the genus.Besides,the closely related group of Roegneria is the genus Brachypodium .Some species of Brachypodium is not only centred in Tangut region,but also their habitats in the region agree with that of the primitive species of the genus.Hence,it was inferred that the Tangue region is likely to be the origin place of Roegneria ,the original time was approximately in the Miocene of Neogene when the Qinghai Xizang Plateau had been raised to a certain height,and the climate in the area had been changed into aridity and coolness.After Roegneria originated from the Tangut region,it further got development and differentiation in some areas of China where the geological activities were violent.However,a few taxa which possess the higher adaptability dispersed to foreign countries in three main routes.The first route is northeastward,and to the Baffin Island via the Bering Straits and Alaska;the second is northwestward,and to the Atlantic seashorn via Kazakhstan and Central Europe;the third is northward,and to the frozen Arctic via Mongolia and Southern Siberia.