Changes in taxonomic and functional diversity of fish communities after catastrophic habitat alteration caused by construction of Three Gorges Dam.

Xin Gao,Huanzhang Liu,Michaela Pawluk,Chen Zhang,Wenxuan Cao,Masami Fujiwara

doi:10.1002/ece3.6320

Abstract

Habitat alterations that result from anthropogenic disturbance impact both the abiotic and biotic conditions of ecosystems, causing changes in biodiversity in many parts of the world. Recently, the use of functional diversity has been suggested as an approach to better evaluate the effects of such disturbance on particular communities. Here, we investigated the temporal changes in species and functional diversities of fish communities in the downstream area of the Three Gorges Dam (TGD) before, during, and after impoundment. We found two regime shifts in the fish community in 2004 and 2013 following impoundment. Although taxonomic diversity declined sharply at the first regime shift, it increased at the second shift. On the other hand, functional diversity declined throughout the same period, indicating the loss of functional diversity despite increased species diversity. Our analysis also showed that the fish communities shifted from under‐dispersion to over‐dispersion due to both a decrease in the relative abundance of migratory fish and an increase in the number of fish adapted to the new hydrologic conditions. Our results indicated that the impacts of dams on downstream fish communities may change over time. Interactions between species may become more important when the environment is stable.

Highlights

Habitat alterations driven by humans are major causes of changes in species biodiversity and community composition (Burlakova et al, 2011; Forister et al, 2010; Tilman, May, Lehman, & Nowak, 1994)
The results of sequential t test analysis of regime-shifts algorithm (STARS) with both window sizes (3 and 5) indicated that the fish community could be separated into three regimes, with the change points identified in years 2004 and 2013 (p < .05) (Figure S1)
The first split isolated 5 years before 2004, and the second split separated two periods (n = 9 and 3, respectively) as the cutoff point in 2013. Results from both STARS and multivariate regression tree (MRT) consistently indicated that the fish communities in Yichang reach could be divided into three regimes: 1999–2003, 2004–2012, and 2013–2015

Summary

Introduction

Habitat alterations driven by humans are major causes of changes in species biodiversity and community composition (Burlakova et al, 2011; Forister et al, 2010; Tilman, May, Lehman, & Nowak, 1994). A functional trait-based approach can better quantify the impacts of dams on ecological communities because ecosystem processes are more directly linked to functional diversity than to species diversity (dos Santos et al, 2017; Lima et al, 2018; Pool, Olden, Whittier, & Paukert, 2010) This is especially true for fishes, for which functional traits such as morphological characteristics (Langerhans, Layman, Langerhans, & Dewitt, 2003; Lujan, German, & Winemiller, 2011; Schlosser, 1982), life-history strategies (Fujiwara, 2007; Mims & Olden, 2012; Olden, Poff, & Bestgen, 2006), and feeding mode (Troia & Gido, 2015; Winemiller, Fitzgerald, Bower, & Pianka, 2015) are closely associated with habitat conditions and food resources. Due to the close relationship between traits of fish communities and habitat alteration, the impact of dams on fish functional composition can be predicted (Arantes et al, 2019)

Methods

Results

Conclusion