湘黔桂交界地区种子植物区系与邻近区系关系的定量研究

QUANTITATIVE STUDY ON THE RELATIOSHIP BETWEENTHE FLORA OF HUNAN-GUIZHOU-GUANGXI BORDER REGION AND THE NEIGHBOURING FLORAS

摘要:

湘黔桂地区与邻近地区种子植物区系各分类等级相似系数为：科的相似系数由大到小依次是南岭、华中、华东、滇黔桂、岭南；属的相似系数依次是华东、南岭、滇黔桂、岭南、华中；种的相似系数依次是岭南、滇黔桂、华中、华东、南岭。科、属、种的相似系数次序不一致的原因可能有三个方面：（1）各比较地区的面积大小不一，在计算相似系数时又没有进行等效面积转换;（2）对各个地区植物资源调查的深浅程度不一；（3）不同分类等级的相似系数在说明区系关系时，其重要性不一样，这可能是重要的原因。在一定范围内的区系比较研究中，种的相似系数能够较好地说明植物区系之间的关系。湘黔桂交界地区与邻近地区种子植物属的地理成分的定量关系是：华中与华东区系以及岭南与滇黔桂区系有密切的关系，而湘黔桂与南岭区系亦密切相关、属的地理成分的树状图表明：湘黔桂与南岭区系有密切的关系，而月，岭南和滇黔桂区系与湘黔桂区系的关系比华巾和华东区系与湘黔桂区系的关系要密切得多，达2倍以上。这些结果与上述各分类等级的相似系数，尤其是种的相似系数的结果相差较大，主要是因为这里指的是属的地理成分之间的定量关系，而非其他等级的相似性。

Abstract:

The region bordering on Hunan, Guizhou and Guangxi Provinccs (HGG) is located in southwest of Hunan, southeast of Guizhou, north and northeast of Guangxi at latitude from 24° 37＇ to 26° 40＇N and longitude from 107° 52＇ to 111° 34＇ E, covering a total area of 70418 km2. Quantitative studics on thc relationship between the HGG flora and the neighbouring floras were made. The results showed that the similarity coeffcients of spermatophyte floras between HGG and neighbouring floras were in order from high to low: Nanling, C. China, E. China, YGG (region bordering on Yunnan, Guizhou andGuangxi Provinces), and Lingnan (south area from the Nanling Mountain) at family level, and E. China, Nanling, YGG, Lingnan and C. China at genus level, while the similarity coeffcientof species was in order Lingnan, YGG, C. China, E. China, and Nanling. The differencesin sequence of similarity coeffcients at family, genus and species levels might be caused by (1) the size of area was different in various comparative regions, and the equivalent area transformation was not calculated, (2) species investigation in various comparative re-gions was not accurate and identical; and (3) similarity coefficients in different taxa for explaining floristic relationship were not alike, which might be an important reason. Family and genus compositions in various comparative regions were obviously different, therefore, the similarity coefflcient at species level could better exhibit floristic relations among floras compared. In terms of geographical elements of genera, the floristic relations between C. China and E. China, Lingnan and YGG were close, while HGG was closely related to Nanling. Dendrogram of geographical elements of genera indicated that close relation occured between HGG and Nanling floras, and the relation of HGG to Lingnan and YGG floras was closer than that to C. China and E. China. The results obtained by geographical elements of genera differed obviously from those by similarity coefficients of family, genus, especially species, the reason of which was that the minimum spanning tree and dendrogram explained only the quantitative relation of geographical elements of genera between floras instead of similarity of other taxa between floras,