Diversity gradients of Neotropical freshwater fish: evidence of multiple underlying factors in human‐modified systems

Abstract

Aim Contemporary patterns of species diversity are the result of a hierarchy of natural processes and modern anthropogenic influences. However, studies of these patterns in human-modified systems from a macroecological perspective are lacking. Considering that fish assemblages in reservoirs reflect both longterm evolutionary responses of species and shorter term responses to anthropogenic stressors, we employed a multi-hypothesis approach using different magnitudes of predictors to analyse the processes that drive fish diversity in reservoirs at a broad spatial scale.Location Brazil.Methods We derived species richness from an extensive database of fish inhabiting Neotropical reservoirs, and using multiple regression analysis, we tested seven hypotheses that link species richness to continuous variables associated with regional, local and population components. We analysed the spatial structure using Moran's I autocorrelation coefficients and used spatial eigenvector mapping to explicitly account for the spatial component when testing the hypotheses by multiple regressions. Partial regressions were performed to map the relative contributions of the different components in explaining species richness.Results Predictors related to six hypotheses were retained in the best-fit models, and our data supported the species-energy, metabolic, species-area, species-distance from the source and time of habitat alteration hypotheses. However, the predictions of the population abundance hypothesis (PAH) were not supported by the data. The shared effects of the different components explained the greatest proportion of the variation in species richness, indicating that distinct mechanisms related to these alternative hypotheses interact or are not spatially independent.Main conclusions Our findings indicate that the latitudinal diversity gradient typically displayed by freshwater fish is maintained in human-modified habitats, such as reservoirs, and that multiple mechanisms drive fish diversity in reservoirs over large spatial scales. The lack of support for the PAH implies that mechanisms structuring diversity patterns can be influenced by anthropogenic stressors.

Temporal changes in fish diversity in lotic and lentic environments along a reservoir cascade

“…Nevertheless, dissimilarity due to species loss was significantly higher in lentic environments with no significant effect of age, showing almost constant rates over time. The construction of a series of dams along a river leads to extreme changes in river landscape that are followed by expected changes in biodiversity (Agostinho et al., ; Bailly et al., ; Ortega et al., ). The greater species loss we detected in the reservoirs suggests that the transformations of a lotic environment into lentic (reservoir) produce a greater impact on fish assemblages than the flow regulation of the lotic stretches downstream of the dams.…”

“…Long‐term modifications in hydrological conditions, following reservoir construction, can result in varied effects on the original fish assemblages (Bailly, Cassemiro, Winemiller, Diniz‐Filho, & Agostinho, ). One consistent pattern is the gradual decrease in native species richness over time observed in reservoirs (Agostinho, Gomes, Santos, Ortega, & Pelicice, ; Orsi & Britton, ).…”

“…Therefore, a better understanding of the effects of reservoir cascades on fish assemblages is necessary, particularly in Brazil, where hydropower represents the country's main energy source. Studies of reservoir cascades in Brazilian rivers have demonstrated that fish composition, richness, and functional diversity change with a longitudinal gradient along the cascade and over time (Ferrareze, Nogueira, & Sartori, 2014;Oliveira, Baumgartner, Gomes, Dias, & Agostinho, 2018;Pelicice, Azevedo-Santos, Esguícero, Agostinho, & Arcifa, 2018;Pereira et al, 2018;Petesse & Petrere, 2012;dos Santos et al, 2017), both in reservoirs (lentic environment) Bailly et al, 2016;Ortega et al, 2018), and also downstream from dams (lotic environment) (Granzotti, Miranda, Agostinho, & Gomes, 2018;de Mérona, Vigouroux, & Tejerina-Garro, 2005;Zdankus, Vaikasas, & Sabas, 2008). Impoundments change the river's flow regime by reducing variability in annual discharge and flood pulses, which in turn impact ecological processes in downstream habitat (Bunn & Arthington, 2002;Pompeu & Godinho, 2006).…”

Effects of regional economics on the online sale of protected parrots and turtles in China

“…These five national conurbations generate approximately half of China's GDP, despite comprising only onetenth of the territory, demonstrating their importance to China's economy. To model regional and economic impacts on the extent of trade among prefectures where the ACE of parrots/turtles sales was ≥1, we used multiple regression (ordinary least squares, OLS) (Bailly, Cassemiro, Winemiller, Diniz-Filho, & Agostinho, 2016). We tested all possible model specifications, and established the best (i.e., the most supported) model according to Akaike's Information Criterion (AICc), following standardized protocols (Burnham & Anderson, 2004;Diniz-Filho, Rangel, & Bini, 2008).…”

Fish functional diversity responses following flood pulses in the upper Paraná River floodplain

“…Impoundments redistribute the river discharge in space and time, increasing minimum and decreasing maximum flows, changing the dynamic and functioning of downstream ecosystems Petts, 1984). The most affected process is the connectivity among microhabitats, which tends to influence the dynamics of species Bailly, Cassemiro, Winemiller, Diniz-Filho, & Agostinho, 2016;Gubiani, Gomes, Agostinho, & Okada, 2007), including the functional diversity (Oliveira, Baumgartner, Gomes, Dias, & Agostinho, 2018;Röpke et al, 2017;White, Ondračková, & Reichard, 2012).…”