试论中国种子植物特有属的分布区类型

ON THE AREAL-TYPES OF THE CHINESE ENDEMIC GENERA OF SEED PLANTS

中国种子植物特有属是局限分布于中国行政区域范围内的植物成分,就其分布特点看,集中分布于中国南部亚热带广阔区域。由于中国地域广袤,虽然大多数特有属分布在东亚自然地域范围内,但南部特有属的分布范围已进入古热带植物区的马来亚森林植物亚区的北部,而西部的特有属的分布范围已进入青藏高原地区。局限于不同地域分布的特有属,各自的起源发生、所经历的地质历史过程存在一定差别。本文以自然地理区划作为研究中国种子植物特有属分布区类型的依据,将中国特有属分布区类型划分为中国东部和中部特有分布变型、中国南部特有分布变型、中国西部特有分布变型和中国北部特有分布变型4类。其中中国南部特有分布变型所含特有属为热带区系成分,其它3个特有分布变型所含特有属为温带区系成分。这样能较客观地反映中国特有属的自然地理特征,有利于研究局部地区植物区系的地质历史演变过程。

The Chinese endemic genera of seed plants, 220 in total, are mainly distributed in China's tropical and subtropical regions. Among them, 132 genera, including Taiwania, Poliothyrsis, Heptacodium and Shaniodendron, are restricted to eastern and central China. These genera are obviously closely related to eastern Asian elements both floristically and phyloge-netically. Seventy-three genera, which mainly occur in southern China, including Hainani-a, Chunia, Tetrathyrium, Sinopanax, Allostigma and Gynogyne , actually have extended their ranges to the areas south of the Tropic of Cancer, and thus reached into the Malaysian Forest Subkingdom of the Palaeotropical Kingdom. They are apparently related to Asian tropical elements. Twelve genera, which occur in western China' s Qinghai-Xizang plateau, are relatively closely related to central Asian elements. The remaining three genera are endemic to northern China, and related to some degree to temperate Asian elements. The present author considers that the Chinese endemic genera of seed plants are heterogeneous in their origin and development and essentially a mixture of several floristic elements. In the light of their distribution patterns in the two kingdoms, seven subkingdoms and 23 regions in China as proposed by professor C. Y. Wu, the author suggests that the distribution of Chinese endemic genera should be divided into four subtypes: (1) Endemic to eastern and central China (15a); (2) Endemic to southern China(15b) ; (3) Endemic to western China(15c); (4) Endemic to northern China(l5d). Floristically, the endemic genera of the subtype 15b, i. e. those endemic to southern China, are tropical elements, and the endemic genera of subtypes 15a, 15c and 15d are all temperate elements. The above division of the endemic genera of seed plants in China can, in the author's opinion, better highlight their geographical characteristics, and thus may bring some new light on the analyses of the historical development of the Chinese endemic genera of seed plants.