确定溪流鱼类多样性的时空分布格局可为鱼类多样性保护与管理提供科学基础。尽管溪流鱼类分类群多样性的纵向梯度格局已有大量报道, 但以鱼类生物学特征为基础的功能多样性研究较少。本文基于2009-2010年4个季度对青弋江1-5级溪流共15个样点的调查数据, 利用形态特征数据和食性构建了鱼类复合功能群, 研究了不同级别溪流间鱼类分类群和功能群组成及多样性的异同, 着重探讨了鱼类分类群和功能群的α和β多样性沿溪流纵向梯度的变化规律。采集到的56种鱼类可分为4个营养功能群和5个运动功能群, 共计14个“营养-运动”复合功能群。双因素交互相似性分析结果显示, 鱼类分类群和功能群组成都随河流级别显著变化, 但季节动态不显著; 双因素方差分析后发现, 鱼类分类群和功能群α、β多样性都随河流级别显著变化, 但受季节影响不显著。经回归分析, 分类群和功能群α多样性与河流级别大小呈显著的线性正相关, 但最大分类群α多样性出现于4级河流, 最大功能群α多样性在4级和5级河流间一致; 分类群和功能群β多样性与河流级别大小呈显著的二项式关系, 呈U型分布。分类群β多样性的空间变化主要取决于物种周转, 而功能群β多样性主要由嵌套所驱动。本研究表明, 沿着“上游-下游”的纵向梯度, 河流鱼类的α和β多样性的空间变化规律不同, 分类群和功能群α多样性的空间格局基本一致, 但分类群(主要是物种周转)和功能群β多样性(主要是功能嵌套)的空间变化过程的驱动机制不同。

Identifying the spatial and temporal patterns of fish diversity in streams is the basis for the conservation and management of stream fishes. The “upstream-downstream” pattern in the taxonomic diversity of stream fish assemblages has been widely studied. However, spatial patterns in functional diversity of stream fishes along longitudinal gradients have been given less attention. Based on data collected in 15 segments representing 1st- to 5th-order streams in the Qingyi River basin during April, July, October 2009 and January 2010, we examined the variations in taxonomic and functional organizations of stream fish assemblages across 1st- to 5th-order streams, and determined the longitudinal patterns of both taxonomic and functional diversities along the stream-order gradient. According to the feeding habits and functional morphological traits, all 56 species collected were divided into four trophic groups, five locomotion groups and 14 combined groups. Two-way crossed ANOSIM showed that both the taxonomic and functional organizations varied significantly across 1st- to 5th-order streams, but did not present significant among-season variation. Two-way ANOVA showed that both α and β diversity of the taxonomic and functional organizations differed significantly with stream order, but not with season. According to the results of regression analysis, α diversity of both the taxonomic and functional organizations had positive linear correlations with stream order, but the maximum α diversity occurred in 4th-order streams. β diversity of taxonomic and functional organizations showed a quadratic distribution (i.e., U-shape) with increasing stream order. The spatial variation in the taxonomic β diversity was mainly driven by species turnover, but variation in the functional β diversity was mainly driven by function nestedness. Our results suggest that, along the “upstream-downstream” gradient, α and β diversity of stream fishes may present different spatial patterns. Although the taxonomic and functional α diversity show similar longitudinal distributions, the ecological processes driving the longitudinal variations in β diversity may be different for the taxonomic (i.e., species turnover) and functional organizations (i.e., function nestedness).