Environmental heterogeneity explains species turnover but not nestedness in fish assemblages of a Neotropical basin

Abstract

Aim: Heterogenous environments can contribute to maintain biodiversity. Traditionally beta diversity studies have focused on determining the effect of environmental variables on the total dissimilarity of species composition. However, decomposing beta diversity in species replacement and nestedness could give new insights on mechanisms affecting spatial patterns of biodiversity. We aimed to answer two main questions about spatial patterns of fish diversity in a Neotropical basin: 1) whether some regions contribute differently to fish diversity, and 2) whether species turnover and nestedness are explained by environmental gradients. Methods Sampling sites in the main channel and tributaries of the Upper Paraná River were sampled between 2013 and 2015. We partitioned beta diversity and tested the relationship of turnover and nestedness with environmental variables. Results 74 species were captured. Some of these species were restricted to different sites, contributing to variation in species composition. Hill numbers showed a trend for higher diversity in the tributaries than in Paraná River sampling sites, and the partition of beta diversity revealed that species replacement drove dissimilarity in species composition. Only total beta diversity and turnover were related to environmental variables, mainly conductivity and turbidity. Conclusions Species diversity and composition of fish assemblages in the Upper Paraná River could be related to environmental gradients. Overall, our results suggest that Paraná River tributaries contribute to increase environmental heterogeneity, and hence to maintain a high diversity and variation in species composition. For that reason, we strongly recommend preserving highly heterogeneous habitats in the region.

Longitudinal patterns in distribution of native and non-native fish species in a regulated temperate Neotropical river

“…As the similarity between reservoir and its downstream reach regarding environmental conditions was high, the observed differences in beta diversity patterns can be mostly attributed to the fragmented habitat conditions imposed by the dam. In our study, beta diversity patterns were mostly explained by species replacement along the longitudinal river axis, a pattern also observed in several tributaries of the upper Paraná River (Peláez et al, 2017). Species replacement refers to the simultaneous gain and loss of species along ecological gradients, when species tend to replace each other (Legendre, 2014).…”

Simplification and replacement of diatom functional traits from a subtropical floodplain lakes paleolimnological records

“…This could explain the different patterns in the variation of the results of functional diversity and beta functional diversity in the two lakes. In addition, the variation of these components in a spatial or temporal gradient may reflect the occurrence and changes of ecosystem processes that may be associated with habitat heterogeneity and niche availability (Melo et al 2009;Peláez et al 2017;López-Delgado et al 2020).…”

Could spatial heterogeneity in flow disturbance drive temporal stability of native–invasive species co‐occurrence in riverscapes?

“…Ecological systems are commonly influenced by environmental spatial heterogeneity, creating geographically patchy habitats (Pickett & Cadenasso, 1995). In freshwaters, much like their terrestrial and marine counterparts, fine‐scale heterogeneity in physical habitat conditions are often associated with higher species richness and spatial variability in assemblage composition, such as amongst stream fishes (Fernandes, Podos, & Lundberg, 2004; Peláez et al., 2017; Smith & Mather, 2013). In contrast, the relationship between coarser scale environmental heterogeneity and assemblage stability is less clear (Fausch et al., 2002).…”