Global patterns and predictors of fish species richness in estuaries

Abstract

Summary1. Knowledge of global patterns of biodiversity and regulating variables is indispensable to develop predictive models. 2. The present study used predictive modelling approaches to investigate hypotheses that explain the variation in fish species richness between estuaries over a worldwide spatial extent. Ultimately, such models will allow assessment of future changes in ecosystem structure and function as a result of environmental changes. 3. A comprehensive worldwide data base was compiled of the fish assemblage composition and environmental characteristics of estuaries. Generalized Linear Models were used to quantify how variation in species richness among estuaries is related to historical events, energy dynamics and ecosystem characteristics, while controlling for sampling effects. 4. At the global extent, species richness differed among marine biogeographic realms and continents and increased with mean sea surface temperature, terrestrial net primary productivity and the stability of connectivity with a marine ecosystem (open vs. temporarily open estuaries). At a smaller extent (within a marine biogeographic realm or continent), other characteristics were also important in predicting variation in species richness, with species richness increasing with estuary area and continental shelf width. 5. The results suggest that species richness in an estuary is defined by predictors that are spatially hierarchical. Over the largest spatial extents, species richness is influenced by the broader distributions and habitat use patterns of marine and freshwater species that can colonize estuaries, which are in turn governed by history contingency, energy dynamics and productivity variables. Species richness is also influenced by more regional and local parameters that can further affect the process of community colonization in an estuary including the connectivity of the estuary with the adjacent marine habitat, and, over smaller spatial extents, the size of these habitats. In summary, patterns of species richness in estuaries across large spatial extents seem to reflect from global to local processes acting on community colonization. The importance of considering spatial extent, sampling effects and of combining history and contemporary environmental characteristics when exploring biodiversity is highlighted.

Predicting fish species distribution in estuaries: Influence of species’ ecology in model accuracy

“…Similarly, temperature has long been regarded as an important structuring factor of estuarine fish species assemblages (Araújo et al, 1999;França et al, 2011a) and according with the present study, its influence on fish species distribution was also noteworthy. Overall, latitude and temperature have been previously reported as determinant predictors of fish diversity among estuaries, at a global level (Vasconcelos et al, 2015). Salinity was also important in explaining fish species distribution and this variable is known to play always an important role in structuring estuarine fish assemblages, as species occurrence may result from their differential tolerance to it (Barletta et al, 2005;Sosa-Lopez et al, 2007).…”

Environmental drivers of taxonomic, functional and phylogenetic diversity (alpha, beta and gamma components) in estuarine fish communities

“…Variables were selected according to their documented effects on fish assemblages (Nicolas et al., ) and their relevance to reflect general ecological hypotheses, e.g. species‐area‐relationship, energy or productivity hypothesis (Henriques et al., ; Vasconcelos et al., ). Five categories of explanatory variables were used to reflect biogeographic, hydroclimatic, marine, estuarine and land cover conditions (a detailed summary is provided in Appendix S1).…”

“…For several years, great advances have been completed to identify processes that drive diversity patterns in estuarine fish communities (e.g. Henriques et al., ; Nicolas et al., ; Sheaves & Johnston, ; Vasconcelos et al., ). However, to our knowledge no study attempted to combine the three diversity facets.…”

“…Therefore, environmental drivers underlying fish communities are linked to local estuarine conditions, as well as to marine, geographic and climatic processes that influence assemblages of marine and freshwater species that can colonize estuaries (e.g. Attrill & Power, ; Henriques et al., ; Vasconcelos et al., ). For instance species richness increases with estuary area and connectivity level with the adjacent ecosystems (Nicolas et al., ; Vasconcelos et al., ).…”

Impact of multiple stressors on juvenile fish in estuaries of the northeast Pacific

“…For future studies, conducting fish sampling contemporaneously with updating of stressor measurements would allow for analysis of dynamic responses. At a global level, patterns of biodiversity can be hierarchical from global to local parameters Vasconcelos et al, 2015), lending credence to continued examination of scale-dependent responses in stressors and their impacts. At a global level, patterns of biodiversity can be hierarchical from global to local parameters Vasconcelos et al, 2015), lending credence to continued examination of scale-dependent responses in stressors and their impacts.…”