Longitudinal Patterns In Taxonomic And Functional Organizations Of Fish Assemblages Of The Headwater Streams Within The Qingyi River

Identifying the spatial and temporal patterns of stream fish assemblages andexplaining them by their surrounding environmental conditions are basic for theconservation and government of fish species diversity. The longitudinal pattern ofstream fish assemblages along the upstream-downstream gradient is recognized asa typically spatial heterogeneity of fishes. This longitudinal patterns of fishassemblages have been widely revealed and been formed by some general rules.However, when compared with fish taxonomic organizations that are based onspecies composition, the functional organizations deriving from the biologicaland/or ecological traits of fishes have received less attention. Till now, thelongitudinal pattern of the functional organizations of stream fishes, especially theeffects of human activities on this pattern, is unclear yet. In this study, based on thedata collected from three streams upper the Chencun Reservoir of the HuangshanMountain during May and October2011, we identified the variations in thetaxonomic and functional organizations of fish assemblages across streams andbetween seasons, examined the correlation between elevation and fish assemblagesand whether this relation differed among streams, and assessed how local habitatvariables affected fish assemblages and their across-stream difference. Our mainresults were as follows:(1) Fish Taxonomic Organizations. Fish species diversity and speciescompositions varied significantly across stream, not between seasons. Speciesdiversity was higher in the Shuxi Stream than that in the Puxi and Maxi Streams.Fish taxonomic organizations in the Shuxi Stream differed from those in the Puxiand Maxi Streams, resulting from the variations of the relative abundance of somespecies. In overall, endemic specialized species, such as Zacco platypus,Acrossocheilus fasciatus and Vanmanenia stenosoma, were more abundant in theShuxi Stream, while some generalized species (e.g., Rhodeus ocellatus, Misgurnusanguillicaudatus, Pseudorasbora prava) were more abundance in the Puxi andMaxi Streams. Significant correlations were observed for elevation and fish speciescomposition and diversity in the Shuxi Stream, but this relation was weakened anddisappeared in the Maxi and Puxi Streams, respectively. In addition, substrate and canopy have revealed to be tightly associated with fish taxonomic organizations inthe Shuxi Stream, however, these habitat variable showed no significant effect onthe organizations in the other two streams.(2) Fish Functional Organizations. The total28species collected were dividedinto four trophic guilds and five morphological guilds based on the cluster analysisfrom the measured data. When combining the trophic and morphological traitstogether,11combined guilds have been recorded. The overall diversity variationsin trophic, morphological and combined organizations were significant acrossstreams and not between seasons, the Shuxi Stream presenting the highest diversitywhile the Maxi Stream the lowest. Based on the two-way crossed ANOSIM,substantial overlapping was observed for fish functional organizations both acrossstream and between seasons; whereas, they significantly differed spatially andseasonally. The functional organizations were the uniform between the Puxi andMaxi Streams, and they differed significantly from those in the Shuxi Stream. Atleast during May, the numbers of trophic and combined guilds, not morphologicalguilds, significantly showed negative relations with elevation. The structures of allfunctional organizations in the Shuxi Stream were significantly determined byelevation; however, this effect of elevation on functional organizations wasweakened and disappeared in the Puxi and Maxi Streams, respectively. Whereassubstrate was revealed to be important in determining the functional organizationsin the Shuxi Stream, which was consistent with the taxonomic organizations, thishabitat variable was not important in affecting those in the Puxi and Maxi Streams.In addition, compared with taxonomic organizations, the functional organizationsshowed higher association with local habitat because our measured habitatvariables were revealed to explain more variance in guilds than in species.Our results suggest that, when looking at a sub-basin scale, human activities(e.g., landuse, river regulation and urbanization) may decrease the diversity andalter the assemblage structures of both taxonomic and functional organizations,may disrupt the longitudinal patterns of taxonomic and functional organizationsalong the upstream-downstream gradient, and may alter the associations betweenlocal habitat and taxonomic and functional organizations of stream fishes.