Beta Diversity Partitioning and Drivers of Variations in Fish Assemblages in a Headwater Stream: Lijiang River, China

Liangliang Huang,Yuanmin Mo,Qi Zou,Erik Jeppesen,Zhiqiang Wu,Naicheng Wu,Jian Huang

doi:10.3390/w11040680

Abstract

Beta diversity partitioning has currently received much attention in research of fish assemblages. However, the main drivers, especially the contribution of spatial and hydrological variables for species composition and beta diversity of fish assemblages are less well studied. To link species composition to multiple abiotic variables (i.e., local environmental variables, hydrological variables, and spatial variables), the relative roles of abiotic variables in shaping fish species composition and beta diversity (i.e., overall turnover, replacement, and nestedness) were investigated in the upstream Lijiang River. Species composition showed significant correlations with environmental, hydrological, and spatial variables, and variation partitioning revealed that the local environmental and spatial variables outperformed hydrological variables, and especially abiotic variables explained a substantial part of the variation in the fish composition (43.2%). The overall species turnover was driven mostly by replacement (87.9% and 93.7% for Sørensen and Jaccard indices, respectively) rather than nestedness. Mantel tests indicated that the overall species turnover (ßSOR and ßJAC) and replacement (ßSIM and ßJTU) were significantly related to hydrological, environmental, and spatial heterogeneity, whereas nestedness (ßSNE or ßJNE) was insignificantly correlated with abiotic variables (P > 0.05). Moreover, the pure effect of spatial variables on overall species turnover (ßSOR and ßJAC) and replacement (ßSIM and ßJTU), and the pure effect of hydrological variables on replacement (ßSIM and ßJTU), were not important (P > 0.05). Our findings demonstrated the relative importance of interactions among environmental, hydrological, and spatial variables in structuring fish assemblages in headwater streams; these fish assemblages tend to be compositionally distinct, rather than nested derivatives of one another. Our results, therefore, indicate that maintaining natural flow dynamics and habitat continuity are of vital importance for conservation of fish assemblages and diversity in headwater streams.

Highlights

Fish assemblages in streams and rivers are, to a large degree determined by the prevailing spatial and environmental conditions, including physical, chemical, and biological characteristics [1,2]
We address three questions: (i) What is most important for fish species composition: spatial variables, environmental variables, or hydrological variables? (ii) What are the major drivers of species and ß-diversity of fish assemblages? (iii) Which factors contribute most to ß-diversity: replacement or nestedness? The hypotheses were that (i) environmental, hydrological, and spatial variables interacted to determine species composition and ß-diversity, and that (ii) spatial variables would be a key driver of ß-diversity, but it was uncertain whether replacement or nestedness would prove to be of superior importance
Our results suggest that environmental filtering is a significant force structuring fish assemblage

Summary

Introduction

Fish assemblages in streams and rivers are, to a large degree determined by the prevailing spatial and environmental conditions, including physical, chemical, and biological characteristics [1,2]. The relationship between fish assemblage and abiotic variables has been intensively investigated, the relative role of different variables contributing to fish assemblage variations remains poorly elucidated [9,10]. Local environmental variables (e.g., nutrients, dissolved oxygen, pH, conductivity) and climate are more often considered to be the key determining factors [5,10]. It is, uncertain which of the abiotic variables (i.e., environmental, hydrological, and spatial variables) best explain the fish assemblage patterns on the regional scale [13,14]. Knowledge of the influence of regional constraints and historical processes on species contribution, abundance, and diversity remain superficial, it has been considered critical for an advance in stream fish ecology and conservation [15,16]

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Results

Conclusion