Biodiversity Science ›› 2018, Vol. 26 ›› Issue (1): 1-13.

• Original Papers: Animal Diversity •

### Longitudinal patterns in α and β diversity of the taxonomic and functional organizations of stream fish assemblages in the Qingyi River

Dong Zhang1, Fengying Wan2, Ling Chu1, Yunzhi Yan1()

1. 1 Provincial Key Laboratory of Biotic Environment and Ecological Safety, College of Life Sciences, Anhui Normal University, Wuhu, Anhui 241000
2 Anhui Normal University Library, Wuhu, Anhui 241000
• Received:2017-10-11 Accepted:2018-01-26 Online:2018-05-05
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# Co-first authors

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).