柽柳科柽柳属的植物地理研究

The Photogeographical Studies of Tamarix (Tamaricaceae)

柽柳属是典型的旧世界温带分布属。对柽柳属 3组 6 8种的分布进行了分析 ,发现本属 3个频度分布中心依次为伊朗 -吐兰区的西亚亚区 (30种 3组 ,其中特有种 13种 ) ,中亚亚区 (2 0种 2组 ,其中特有种 6种 )和地中海区 (12种 3组 ,其中特有种 6种 )。由于伊朗-吐兰地区的西亚亚区存在本属最多的组与种、特有种多且可以见到柽柳属系统发育系列 ,因而认为该亚区是现存本属植物的现代分布中心和分化中心。地中海地区包含的组、种数仅次于伊朗 -吐兰区 ,并且特有种为 6种 ,带有新特有种的性质 ,全是系统发育上相对年轻、进步的类型 ,被认为是本属的一个次级分布中心 ,另一个次级分布中心在中亚亚区 ,尤其是中国西北干旱地区。根据柽柳属植物的现代地理分布、化石资料及地质历史资料 ,推测柽柳属起源于古地中海热带成分盛行的早第三纪始新世 ,具有起源古老的性质 ,并且随着晚第三纪古地中海的退缩、气候逐渐干旱而得到进一步发展 ,产生许多新的以温带成分为主适应旱生环境的现代柽柳属种类。柽柳属起源之后 ,首先繁衍、散布到以伊朗为中心的现代分布中心 ,其后以伊朗为廊道向西、向东扩散 ,在地中海沿岸、东非、阿拉伯半岛、非洲西南部及亚洲中部的荒漠地区得到发展。

Tamarix L. is a genus with the distribution pattern of Old World Temperate.The distribution patterns of 3 recognized sections covering 68 species in Tamarix are analyzed, and the result showet that the three centers of frequency distribution possessed with diffesent quantities of species:the W.Asia subregion of Irano-Turanian Region (30spp./3sects.,including 13 endemic species), the C.Asia subregion of Irano-Turanian Region (20spp./2sects.,including 6 endemic species), the Mediterranea Region(12spp./3sects.,including 6 endemic species). In the light of the fact that most taxa including the primitive and advanced ones, and the most taxa including the primitive and advanced ones in Tamarix occur in the W.Asia.The W.Asia subregion of might be the center of diversity and distribution of the genus. As the Mediterranea Region and C.Asia Subregion of were just second to that of W.Asia subregion in number of sections and species,and many endemic species also appeared in these regions, they were considered as the secondary centers of distribution and speciation of the genus. Based on available fossil record of the genus and the historical data of geology, we speculate that Tamarix had already existed during Eocene when the land masses on the both sides of the ancient Mediterranean Sea (the Tethys) were populated by the xerothermic floral elements, by the sea retreat and climates turn dry afterwards, the species, dominated by temperate zone flora and adaptive to arid environment, developed greatly. When the genus was generated, they invaded to Iran plateau and migrated to the east and west just take Iran as a corridor, and took a further development in the arid zone of W.Africa,S.W. Africa, Arabian peninsula and C.Asia. In a word, the retreat of the Tethys, uplift of Himalayan Mts. and alteration of glacier has play an important role in the formation of modern distribution pattern of the genus Tamarix L.