澜沧江-湄公河中上游淡水鱼类多样性

澜沧江-湄公河是东南亚最大的河流, 也是世界上淡水生物多样性最高的三大河流之一。由于特殊的地理位置和国际河流属性, 澜沧江-湄公河淡水鱼类的多样性现状仍缺乏系统的认识。本文在近20年调查的基础上, 系统整理了澜沧江-湄公河中上游32个支流或亚流域的淡水鱼类物种名录, 在此基础上对其种类组成和分布进行了分析, 并利用分类学多样性指数对澜沧江-湄公河中上游流域的物种多样性进行了评估。结果表明, 澜沧江-湄公河中上游共记录了淡水鱼类745种, 分属于2纲17目63科229属, 其中鲤形目鱼类451种, 占物种数的60.5%。分类学多样性指数显示, 从源头到中游, 淡水鱼类在分类阶元上的分布越来越均匀, 亲缘关系越来越远, 分类多样性越来越高。聚类分析(cluster analysis, CA)和多维尺度分析(multi-dimensional scaling, MDS)表明, 当Jaccard相似性系数为8.69时, 澜沧江-湄公河中上游32个亚流域可以分为源区、上游和中游3组; 相似性分析(ANOSIM)结果显示, 各组之间淡水鱼类组成差异显著(R = 0.877, P = 0.001)。相似性百分比分析(similarity percentage analysis, SIMPER)结果表明, 导致3组差异性的鱼类主要是鲤形目和鲇形目鱼类, 且随着地势阶梯的升高出现了科级、属级类群的替代。近几十年来, 随着流域各国人口的增长和经济的快速发展, 澜沧江-湄公河鱼类多样性和渔业资源面临严重威胁, 未来需加强流域内国家间合作, 在流域尺度上制定科学保护计划。

Freshwater fish diversity in the upper and middle reaches of the Lancang-Mekong River

The Lancang-Mekong River is the longest river in Southeast Asia, and is one of the richest areas of freshwater biodiversity in the world. Because it is an international river through six countries and holds extremely high fish biodiversity, there is a lack of systematic understanding of freshwater fish diversity. Over the past two decades, this team systematically compiled a list of freshwater fish species in 32 sub-basins or tributaries in the upper and middle reaches of the Lancang-Mekong River. Now in this paper, the species composition and distribution of fish have been analyzed, and the species diversity of the upper and middle reaches of the Lancang-Mekong River has been evaluated using the taxonomic diversity index. The results showed that 745 species of freshwater fish were recorded in the middle and upper reaches of the Lancang-Mekong River. These fish belong to 229 genera, 63 families, 17 orders and 2 classes. Of these, 451 species of Cypriniformes fish accounted for 60.5% of the species. The taxonomic diversity index showed that, from the source to the middle reaches of the river, the taxonomic distribution of freshwater fish became increasingly more even, the relationships were increasingly further apart, and the fish diversity gradually increased. Cluster analysis (CA) and multi-dimensional scaling analysis (MDS) results showed that the 32 sub-basins could be divided into three groups (Jaccard similarity coefficient=8.69), and the analysis of similarity (ANOSIM) indicated that the composition of freshwater fish differed significantly between the groups (R = 0.877, P = 0.001). Similarity percentage analysis (SIMPER) results indicated that Cypriniformes and Siluriformes were the main fish that differed among the three groups, and the species composition of groups presented distinctive changes at the family and species levels with the altitude rising. With the rapid population growth and economic development of the countries in the river basin in recent decades, the fish diversity and fishery resources of the Lancang-Mekong River face serious threats. Thus, it is urgent that countries in the river basin cooperate and formulate a scientific protection plan at the basin scale.