# Changes in Fish Taxonomic and Phylogenetic Diversity and Their Driving Factors in a Reservoir in the Karst Basin of Southwest China

## TL;DR

This study explores how dam construction affects fish diversity in a Chinese reservoir, showing that environmental changes and spatial factors influence community patterns.

## Contribution

The study reveals how dam construction alters relationships between taxonomic and phylogenetic diversity and highlights the role of environmental and spatial factors in community assembly.

## Key findings

- Fish taxonomic and phylogenetic β-diversity was low with high turnover patterns.
- Environmental heterogeneity strongly influenced taxonomic and phylogenetic diversity and turnover.
- Spatial structure primarily affected nestedness processes in fish communities.

## Abstract

We examined changes in the environmental characteristics of reservoir impoundment and analyzed patterns of fish taxonomic and phylogenetic α- and β-diversity. A few significant relationships between taxonomic and phylogenetic α-diversity indicated that considering only the diversity of a single dimension might lead to deviations in results and conclusions. The formation of reservoir impoundment increased taxonomic and phylogenetic similarity. The importance of community assembly mechanisms varied based on the ecological processes measured; total β-diversity and the turnover process for taxonomic and phylogenetic indices were primarily influenced by environmental heterogeneity, while the nestedness process was predominantly affected by spatial structure. Our findings highlight that dam construction alters the relationships between taxonomic and phylogenetic α-diversity from different perspectives and enhances community similarity, thereby providing a foundation for managing hydraulic infrastructure projects and conserving biodiversity.

Dam construction can significantly alter local habitat characteristics and the distribution patterns of aquatic organisms. However, the variations in the multidimensional diversity of fish assemblages in reservoirs, as well as the relative significance of potential community assembly rules, remains poorly understood. This study elucidated the patterns of taxonomic and phylogenetic α- and β-diversity with its decomposition components (i.e., turnover and nestedness) of fish assemblages in the Dongfeng Reservoir, situated in the karst basin of southwest China. Additionally, we evaluated the relative importance of environmental heterogeneity and spatial structure. We found significant nonlinear relationships (p < 0.05) between taxonomic and phylogenetic richness. Both fish taxonomic and phylogenetic β-diversity values were low (<0.33) with high turnover patterns (72.23% and 67.42%), underscoring the necessity for local managers to protect entire water areas to maintain or enhance community diversity. Only taxonomic and phylogenetic richness are significantly positively (e.g., water depth) and negatively (e.g., turbidity) affected by different environmental variables. Environmental heterogeneity was the dominant factor influencing both total β-diversity and turnover processes at the taxonomic and phylogenetic levels, while spatial distance primarily influenced the nestedness process. These findings are critical for elucidating changes in patterns of fish community diversity and their driving factors in the context of dam construction, providing a foundation for the conservation and management of aquatic organisms in other rivers, lakes, and reservoirs.