河西阿拉善内流区的鱼类区系和地理区划

FISH-FAUNA AND ZOOGEOGRAPHICAL DIVISION OF HEXI-ALASHAN REGION, THE NORTHWEST CHINA

中国西北河西阿拉善内流区,主要含石羊河、弱水、疏勒河三个分离的内陆水系,为一独立的水文单元,面积逾50万平方公里,天然分布了鲤科2属2种、鳅科条鳅亚科2属10种。组成鱼类区系的这12个土著种中,有7种/亚种为本区特有。10种无鳞条鳅和河西花斑裸鲤表征了本区和中亚山地及青藏高原的共同鱼类区系特征:区系组成简单,裂腹鱼类和无鳞条鳅类占优势,很少凶猛种类,适应高寒水体严酷环境的种类特化,和局限分布的类群分化。鲫的存在体现了本区处在青藏高原和中亚内陆干旱区边缘的特点。这些鱼类在本区也表现出水平和垂直分布的差异。 平均动物区系类似性(AFR)判别和数值聚类分析,从表相学全面相似性上阐明,本区三水系形成以弱水为中心的独立鱼类地理学单位,与柴达木盆地的区系关系最密切。特有性俭吝分析(PAE)和俭吝性种系发生分析(PAUP)产生了基本一致的区域支序图,从分替论的鱼类地理亲缘上揭示了:疏勒河与弱水,它们与石羊河,河西与柴达木(和河曲区即黄河上游),它们与青海湖是一系列姐妹群关系,一起组成一个大的区域单系群;而陇中与河套,它们与内蒙古高原,又依次为姐妹群关系,一起组成另一大的单系群;两大单系群作为姐妹群,形成更高一级区域单系群。 进而结合有关的鱼类种系发生和区域地质历史资料。

As an independent hydrological unit, Hexi-Alashan Region of the northwestern China is an area of more than 500000 square kilometers and contains principally three separated inland river systems, namely, Shule River, Ruoshui River anl Shiyang River. There are fishes of 12 species/subspecies, 4 genera and 2 families (Cobitididae and Cyprinidae) naturally distributed in the region and 7 in 12 are endemio. Ten species of scaleless noemacheilini fishes and Gymnocyprinus eckloni chilianensis characterize the features of fish-fauna of the region shared with Qinghai-Tibet Plateau or High Central Asia: simpler faunal components, fishes Schizothoracinae and scaleless Noemacheilinae in dominant position rare pedatory fishes, specialized to adapt to the harsh conditions of water bodies with high altitude and low temperature, and fish taxa differentiated due to local and limited distribution. The distribution of Carassius auratus in the region is a feature of the region's position at the margin of Qinghai-Tibet Plateau and the border of the arid inland region of Central Asia. The fish distribution also displays horizental and vertical geographical differences in the region.In phenetic overall similarities, the descrimination and the cluster analysis of average faunal resemblance (AFR) indicate these three river systems male up an independent ichthyogeographical unit, with Ruoshui River as its center and most closely related to Qaidam Basin faunally. PAE and PAUP give two area cladograms basically consistent and, basing on the vicariance theory, reveal the fish geographical relationships as following: Shule River and Ruoshui River, they and Shiyang River, Hexi Area and Qaidam (as well as Hequ, i.d., the Upper Huang He River), anl all of them and Kuku Nut Lake are a series of sister area groups, or in other words, they are all in a large monophyletic area group. While Longzhong and Hetao, and they and Inner Mongolia Plateau are also sister area groups and all of them make up other large monophyletic area group. Then these two large area groups are sister area groups and make up a monophyletic area group at a higher level.Furthermore, the evolutionary history of the fish fauna of Hexi-Alashan Region is recounted in the light of the phylogeny of the fishes and the data of the geological history of the area. It is elucidated that mainly the tectonic movements, especially the Himalaya Movement, and the climatic changes since Tritary Period have resulted in the area vicariance of HexiAlashan Region and the isolation of the river systems, the long-termed isolation has caused the differentiation of the fish taxa and thus the modern pattern of fishes distribution is determined in this region.Then the problem of the zoogeographical division is considered for the fresh-water fishes distributed in the Northwest and Hequ-Qilian Province is suggested to enlarge and replace Maqu Province, which is situated in the northeastern part of Qinghai-Tibet Plateau, to the north of Bayan Khara Mountains and East Kunlun Mountains, including four sub-divisions (Biogeographical Prefectures) Hexi-Alashan, Qaidam, Hequ, and Kuku Nur Lake, and suboradinating to High Central Asia Region or he Northwest Plateau or West China Region. Finally, it is pointed that the approach PAE is one merit to be applied to the research on biogeographical problems in China.