A SURVEY ON THE AQUATIC VASCULAR PLANTS OF THE PEARL RIVER BASIN IN GUANGDONG

There are 131 species of aquatic vascular plants in the Pearl River basin in Guangdong Province. They belong to 81 genera of 44 families. Among them, 111 species are found in the Pearl River Delta, 75 species in the Xijiang River(West River), 67 species in the Dongjiang River(East River), and 57 species in the Beijiang River(North River). The geographical distributions of these species are as follows: 41.9%(55 species)of the aquatic nvacro-phytes in the Pearl River basin have worldwide distributions; 27%(35 species)have distributions in the tropical Asia; 12%(16 species)have distributions in the tropical-subtropical zone; 16%(21 species)have distributions in the tropical-temperate zone; 3%(4 species)have distributions in the temperate zone.The species with distributions in the tropical Asia are second important in number(27%), only next to the group with world-wide distributions. However, only about ten of them, Including Kandelia cande, Aegiceras corniculatum, Cyperus malaccensis var. brevifolius.... etc., constitute of dominant species of the mangrove vegetation and aquiherbosa of the estuary of the Pearl River. Other species with distributions in the tropical Asia are sparsely distributed in the Pearl River basin and are not as important as the previous ones; they afe members of the tropical flora dispersed into the subtropical zone.Although species with tropical-subtropical distributions constitute only 12% of the total number, many of them are dominant species of this area. They have wide distributions, and high growth and reproduction rates. Together with those with distributions in the tropical-temperate zone(16%), they form the major part of the tropical macrophytes in South Asia.Species with distributions in the temperate zone make up only 3% of the total number and have minor influence on the aquatic macrophytes of this area.