西双版纳植物区系的特点与亲缘

西双版纳植物区系经初步资料整理统计有种子植物 3336种 ,隶属于 1 1 4 0个属 ,大约 1 97个科。植物区系成分构成是热带分布的科和属分别占总科和属数的 60 .1 %和 83.5% ,在热带分布属中 ,又以热带亚洲成分占优势 (占 32 .8% )。通过植物区系组成和地理成分分析 ,认为该植物区系是热带性质的 ,属于热带亚洲区系的一部分 ,并带有明显热带边缘性质和几种地理成分交汇的特点。西双版纳植物区系与广西热带植物区系和海南热带植物区系在发生上同源 ,主要来自于古南大陆与古北大陆区系成分的融合 ,在发展上受热带亚洲植物区系的渗透和强烈影响。

Characteristics and affinity of the flora of Xishuangbanna,SW China

The flora of Xishuangbanna,SW China,is recorded to consist of 3 336 native seed plant species belonging to 1 140 genera and 197 families,of which the family Ochidaceae with 334 species is the largest family in size;Papilionaceae with 182 species is the second;Rubiaceae with 147 species is the third;and other families are ranked as following:Gramineae(143 species),Euphorbiaceae(119),Compositae(107),Moraceae(77),Urticaceae(72),Lauraceae(68),Zingiberaceae(67),Asclepiadaceae(62),Apocynaceae(61),Labiatae(59),Annonaceae(52),Cucurbitaceae(50),Acanthaceae(49)Rosaceae(49),Fagaceae(45),Araceae(43)etc. The statistics of distribution patterns of taxa shows that the families and genera of tropical distribution make up 60 1% and 83 5% of the total sum of the flora separately. Furthermore,the genera of tropical Asian distribution contribute 32 8% of the total sum of genera which represents strong affinity to tropical Asian flora. It is confirmed that the flora of Xishuangbanna is of the tropics in nature and as a part of the tropical Asian flora. Occurred at the montane habitats from northern margin of tropical Asia,the flora also shows conspicuous characters of the tropical margin and is the transitional to the subtropical flora of SW China. It is concluded that the flora of Xishuangbanna has the same origin as the floras of the tropical Guangxi and Hainan of S China and was possibly derived from the ancient Gandwana and Laurasian elements,but strongly affected by modern tropical Asian flora.