Regional species richness, hydrological characteristics and the local species richness of assemblages of North American stream fishes

Abstract

Summary 1. Local assemblage structure, from a deterministic perspective, is presumably dictated by the regional species pool as well as regulated by local factors. We examined the relationships of the regional species pool and local hydrological characteristics to local species richness of North American freshwater fishes using data sets collected during the National Water Quality Assessment program conducted by the United States Geological Survey. 2. We predicted that local species richness is ultimately constrained by the composition of the regional species pool and further associated with local hydrological factors. Moreover, we predicted that variation in local species richness within major families can be explained by different combinations of hydrological characteristics that represent lineage‐specific responses to the environment. 3. Daily discharge and regional and local species richness data were assembled from 41 stream localities across the United States. Multiple stepwise regressions were conducted to predict local species richness, based on regional species richness, mean discharge and hydrological characteristics quantified by nine variables characterising flow variability. Species richness at each site was calculated for the entire assemblage as well as within the four most species‐rich families in the data set (Catostomidae, Centrarchidae, Cyprinidae and Percidae). 4. Local species richness was best predicted by a combination of regional species richness and discharge magnitude when all species were considered. Regional species richness was a significant explanatory variable of local species richness for three of four families (Catostomidae, Centrarchidae, Cyprinidae), but not for Percidae. Local richness in Centrarchidae and Cyprinidae was positively correlated with temporal flow variability as well as high and low flow duration, respectively, while richness in Catostomidae and Percidae tended to be associated with discharge volume. In addition, local species richness for three of the four major families was positively correlated with species richness of the other families in the assemblage, potentially suggesting the influence of local habitat quality and heterogeneity. 5. Results suggest the importance of the combined influences of the regional species pool and local hydrological characteristics on local richness in freshwater fishes, with variation in richness within each family predicted by different characteristics of flow regimes.

Using watershed‐scale hydrological models to predict the impacts of increasing urbanization on freshwater fish assemblages

“…However, flow variability (CV) was an important predictor of variation in species richness only for Centrarchidae and Cyprinidae, with opposite impacts on species richness in each group. These results, particularly related to flow variability, confirmed the need to recognize the importance of differential taxonomic responses to environmental variability (Chinnayakanahalli et al , ; Knouft and Page, ; Niu et al , ).…”

“…Increases in flow can increase stream connectivity and create larger and more stable habitats for fishes (Schlosser, ), whereas increases in flow variability can have varying effects on species richness depending on the degree of flow variability and individual species' tolerance to this variation (Niu et al , ). Species richness was positively correlated with flow in all analyses (all species, Centrarchidae, Cyprinidae, and Percidae).…”

“…The spatially explicit nature of the hydrological modelling efforts of Chu et al () allows for the identification of the most vulnerable sites in the watershed. Although increases in flow across sites tend to be associated with increases in fish species richness both within and among drainages (Vannote et al , ; Niu et al , ), the impacts of increases in flow variability are not as consistent, especially among particular taxonomic groups. Consequently, we expect that flow will be positively correlated with species richness and predicted impacts of changes in flow variability will vary among taxonomic groups, thus resulting in a mosaic of levels of vulnerability among sites across the watershed.…”

Hydrologic characteristics, food resource abundance, and spatial variation in stream assemblages

“…The positive correlation between flow variability and fish species richness was consistent with patterns reported for Cyprinidae in North American (Niu et al, ). A trait based framework demonstrated that natural flow variability favors species exhibiting opportunistic and equilibrium life history strategies (Winemiller, ; Mims and Olden, ).…”

“…This time span permits estimation of biologically relevant hydrologic indices such as inter‐year coefficient of variation and mean rising rate of high flow events, and is comparable to the life spans of most fish species in the region (Pflieger, ). Nine hydrologic indices were calculated to characterize flow variability at each sampling site using the Indicators of Hydrologic Alteration software (IHA; The Nature Conservancy, ; as used in Niu et al, ; see Appendix SII).…”