Abstract:

Understanding differences in aquatic biodiversity and its driving forces among various river network positions is valuable for guiding effective conservation practice. Although some researchers addressed this question, most studies focused on comparing differences in the number of species (i.e., species richness), without considering differences in the distribution pattern of communities and their related factors. In the present study, the positions of the river network were divided into the edge of the river network and the center of the river network. we surveyed the diversity of benthic macroinvertebrates in the Liujiang River network and compared differences in macroinvertebrate species richness, density, dominant taxonomic units, and community compositions between the edge and center position sites of the river network, as well as differences in relationships between community compositions and environmental and spatial factors. We found that a total of 132 taxonomic units of benthic macroinvertebrates were collected in this survey, among which 109 taxonomic units of insecta were the dominant units. The average taxonomic units (32) and community density (2.29×10³ ind·m⁻²) of benthic macroinvertebrates at the edge sites were both higher than those of the center sites (average taxonomic units: 22, community density: 1.04×10³ ind·m⁻²). There were 12 taxonomic units with an average abundance higher than 1%. Among these dominant units, the average relative abundances of Ephemeroptera were higher at the edge sites, while Chironomidae were more abundant at the center sites. Dissolved oxygen and water depth affected macroinvertebrate communities across all surveyed sites. In addition, community compositions were also influenced by chemical oxygen demand at the edge sites and by total nitrogen and flow velocity at the center sites. Both environmental and spatial distances influenced β diversity of benthic macroinvertebrates at the edge sites, while β diversity at the center sites was mainly driven by environmental distance. Our findings suggest that different conservation strategies should be implemented for the edge and center positions within the Liujiang River network to protect benthic macroinvertebrate biodiversity.

Key words: river network positions, benthic macroinvertebrate, environmental factors, spatial factors, biodiversity, β diversity, community pattern

摘要：

了解不同河网位置的水生生物多样性差异对于识别生物多样性重点保护区域具有重要指导意义。虽然已有部分研究关注河网位置对水生生物多样性的影响，但这些研究大都集中于比较物种数量的变化，而对群落组成的影响差异研究较少。该研究将河网位置分为河网边缘和河网中心，基于柳江大型底栖动物的调查数据，比较河网边缘、中心位置的大型底栖动物分类单元数量、密度、优势分类单元以及群落组成相异度及其与环境和空间因子关系的差异。共采集到大型底栖动物132个分类单元，其中昆虫纲109个分类单元，为优势类群。河网边缘、中心位置样点分别采集到大型底栖动物129和114个分类单元，河网边缘样点的大型底栖动物平均分类单元数（32个）和平均密度（2.29×10³ ind·m⁻²）均显著高于中心位置样点（平均分类单元数：22个，平均密度：1.04×10³ ind·m⁻²）。此外，有12个分类单元的平均相对丰度超过1%，其中，蜉蝣目在河网边缘的平均相对丰度高于河网中心，双翅目在河网边缘的平均相对丰度低于河网中心。柳江河网边缘位置的大型底栖动物群落组成主要受溶解氧、化学需氧量和水深等环境因子的影响，而溶解氧、总氮、流速和水深是影响河网中心位置大型底栖动物群落组成的主要环境因子。大型底栖动物β多样性在河网边缘受环境因子和空间因子的共同影响，在河网中心则主要受环境因子的影响。结果表明，河网边缘与中心位置的河流大型底栖动物群落组成及其影响因子有显著差异，应该采取不同的保护策略。

关键词: 河网位置, 大型底栖动物, 环境因子, 空间因子, 生物多样性, β多样性, 群落格局