长江中游干流鱼类群落构建机制分析

研究选取长江中游5个采样点(宜昌、枝江、荆州、汉南、湖口)为代表, 采用系统发育群落结构方法分析了不同空间尺度下长江中游鱼类群落的构建机制。结果表明: (1)空间聚类分析显示, 在65%的相似性水平上, 所有样点可以划分为3个Group: GroupⅠ(宜昌)、GroupⅡ(枝江+荆州)和Group Ⅲ(汉南+湖口)；在55%的相似性水平上, 所有样点可以划分为2个Group: Group A(宜昌)和Group B(枝江+荆州+汉南+湖口), 且聚类分析结果与采样点的空间分布相符合。(2)在不同空间尺度下, 鱼类群落构建机制存在差异: 从地区采样点尺度来看, 荆州江段鱼类群落表现为竞争作用主导群落构建, 其余采样点鱼类群落均为环境过滤作用；从区域尺度来看, 宜昌江段鱼类群落表现为环境过滤作用的建群机制, 其余4个采样点在扩大空间尺度后, 即分为Group A和Group B的情况下, 其鱼类群落构建机制转变为物种间竞争作用。因此, 长江中游干流鱼类群落构建机制表现了地区环境和空间尺度的共同作用。由于水流湍急, 宜昌始终表现为环境过滤作用。其他江段在采样点尺度多数表现了环境过滤作用, 但是在宏观的空间尺度上, 却由于空间异质性的增加, 容纳了远缘的物种, 群落构建机制转换为竞争作用。这样的转变有别于陆生植物中由小尺度竞争作用转为大尺度环境过滤作用的情况。

MECHANISM OF FISH COMMUNITY ASSEMBLY IN MIDDLE REACHES OF THE YANGTZE RIVER

Community assembly mechanisms have long been a central issue in ecology. Three mechanisms have been proposed to govern community assembly: neutral process, competitive interaction, and environmental filtering. To explore the assembly mechanism of fish communities in the middle reaches of the Yangtze River, we collected fish samples from 5 reaches (Yichang, Zhijiang, Jingzhou, Hannan, Hukou) and conducted a series of analysis including phylogenetic community structure analysis. The results showed that: (1) spatial clustering analysis revealed that all sampling reaches were identified as 3 groups (Yichang, Zhijiang + Jingzhou, Hannan + Hukou) with a similarity level of 65% or 2 groups (Yichang, Zhijiang + Jingzhou + Hannan + Hukou) with the similarity level of 55%. These groupings were consistent with the spatial distribution of the sampling reaches; (2) The assembly mechanisms of fish communities were distinct at different spatial scales. At local scale, competitive interaction drove the fish community assembly in Jingzhou sampling reach, while environmental filtering drove the fish communities assembly in other sampling reaches. At regional scale, environmental filtering structured the fish community in Yichang sampling reach, while interspecific competition structured the fish communities in the other 4 sampling reaches. Therefore, the local environment and spatial scales play a role simultaneously during fish community assembly in the middle reaches of the Yangtze River. The fish community in Yichang reach is structured by environmental filtering, which may be due to the swift current there. In other reaches, environmental filtering drove the fish community assembly at local scale, while competitive interaction played key role at regional scale. This may be because as spatial heterogeneity increases, distantly related species were contained in the community assemblage. This phenomenon is different from those in terrestrial plant communities, where the assembly mechanism has changed from small-scale competitive interaction to large-scale environmental filtering.