THE TROPICAL FLORA OF SOUTHERN YUNNAN, CHINA, AND ITS BIOGEOGRAPHIC AFFINITIES

Zhu, Hua

ANNALS OF THE MISSOURI BOTANICAL GARDEN

2008

95

4

Zhu, H

The flora of Xishuangbanna in southern Yunan, southwestern China, consists of 3340 native seed plant species belonging to 1176 genera and 182 families. Tropical floristic elements at the generic level form a major contribution (78.3%) to the total flora of southern Yunnan, of which the dominant geographic elemenmts are those of tropical Asian distribution. The tropical Asian flora of Xishuangbauna is similar in composition to other tropical floras from Yunnan, especially in the families with the most species richness. These regional floras have similarities of more than 89% at the family level and more than 76% at the generic level, but share only 43%-50% similarity at the specific level. Comparison with mainland Southeast Asia (Thailand) and Malesia (Malay Peninsula) floras reveasl that most of the dominant families from southern Yunnan are also dominant in mainland Southeast Asian and Malesian floras. The floristic similarities between the flora of southern Yunnan and those of tropical Asia are more than 80% at the family level and more than 64% at the generic levelk. This suggests that the tropical flora of southern Yunnan has a close affinity with tropical Asian flora and supports the idea that the flora of southern Yunnan. together with mainland Southeast Asian flora, belongs to the Indo-malaysian floristic subkingdon of the Palcotropoical kingdom as suggested by Takhtajan, or the Malaysian subkingdon of the Palcotropical kingdom as suggested by Wu and Wu. However, situated at the northern margin of tropical Asia, the flora of southern Yunnan comprises less strictly tropical elememts compared to Malaysian flora and consequently, represents only a marginal type of Indo-Malaysian flora. The tropical flora of southern Yunnan is supposed to be derived from tropical Asian flora with the formation of the eastern monsoon climate after the Tertiary.