A DISCUSSION ON BIOGEOGRAPHICAL LINES OF THE TROPICAL-SUBTROPICAL YUNNAN

摘要

Based on comparative studies on four regional floras from northwest, west, south and southeast of Yunnanrespectively, the formerly suggested two biogeographical lines, i.e. the "Tanaka Line" and the "Ecogeographical Diago-nal Line", both going from northwest to southeast of Yunnan, and their significance are discussed. In family and genericlevels, similarity coefficients among the four compared floras are more than 93% and 60% separately, which indicate theclose floristic affinities among them. The highest similarity coefficient, i.e. 98.7% in family level and 78.6% in gener-ic level separately, is found between the regional flora of northwest Yunnan and the flora of southeast Yunnan althoughthese two regions are the most distant away each other among the compared regional floras. The flora of northwest Yun-nan is also the most similar to the flora of southeast Yunnan in floristic composition. These support the idea of"Ecogeographical Diagonal Line". In specific level, the relatively high similarity coefficient is between the regional floraof west Yunnan and the one of south Yunnan. The floristic affinities among these regional floras and some distributionpatterns could be explained by the geological history and tectonic theory of Yunnan.