Environmental heterogeneity and dispersal limitation explain different aspects of β‐diversity in Neotropical fish assemblages

Abstract

From a metacommunity perspective, patterns of β‐diversity emerge from the interplay between spatial and environmental processes. For obligate aquatic dispersers, river network constraints can be reflected in diversity patterns. Here, we aimed to determine the effects of environmental heterogeneity and spatial connectivity on β‐diversity components. We sampled fish assemblages in 21 sites across a longitudinal gradient. Beta‐diversity for taxonomic and functional composition among sites was decomposed into its turnover and nestedness components. We investigated whether environment was more important to functional β‐diversity and spatial factors had a higher contribution to dissimilarity in species composition. Further, we tested whether environmentally homogeneous sites with higher spatial connectivity showed lower compositional changes. We found that spatial factors were more important for taxonomic β‐diversity, whereas environment explained functional dissimilarity among habitats. Although environment and spatial factors contribute to total β‐diversity, they explained different components: while environment explained a higher portion of turnover, spatial factors were related to nestedness. The effects of mere spatial isolation and directional connectivity differed for species and functional β‐diversity and for the components of β‐diversity. Including directionality in spatial connectivity enabled the explanation of a higher proportion of variation of total species β‐diversity and its turnover. Our results suggest that niche and spatial processes may influence differently taxonomic and functional β‐diversity components. Thus, habitat filtering was the primary mechanism affecting functional diversity and species turnover, whereas spatial connectivity drove species nestedness.

The drivers of multiple dimensions of stream macroinvertebrate beta diversity across a large montane landscape

“…This finding may occur because different sites are characterized by distinct environmental heterogeneity, so that assemblages with low trait diversity occurring at less heterogeneous sites are likely to be subsets of the high trait diversity assemblages that exist in highly heterogeneous sites (Rocha et al 2019). In line with our expectation and other trait‐based studies (Li et al 2019; Peláez and Pavanelli 2019), functional beta diversity (the overall and turnover components) was more strongly associated to local environmental variables. This indicates, as elaborated in the Habitat Templet Theory, that local environment conditions directly select species with specific trait combinations, but not species identity or lineages per se, to coexist within local assemblages (Southwood 1977).…”

“…As we expected, different dimensions of beta diversity showed various responses to the focal ecological factors, as also found in previous studies conducted in lentic (Heino and Tolonen 2017; Fu et al 2019) and lotic ecosystems (Li et al 2019; Peláez and Pavanelli 2019). Our results showed that both taxonomic and phylogenetic beta diversities were mainly contributed by turnover, and were more strongly affected by spatial factors (i.e., dispersal limitation).…”

“…We also conjectured that the relative importance of explanatory factors depended on the beta diversity dimensions considered. Specifically, spatial factors may be more important for taxonomic and phylogenetic beta diversities (Leaopires et al 2018;Pelaez and Pavanelli 2019), whereas local environmental variables should be more influential for functional beta diversity (Li et al 2019;Rocha et al 2019).…”

“…Taxonomic, functional, and phylogenetic beta diversities may respond differently to the focal environmental and spatial factors (Peláez and Pavanelli 2019). Generally, taxonomic beta diversity is thought to be generated by the combined effects of environmental filtering and spatial processes (Gianuca et al 2017 b ).…”

Survey of fish species from the Lower Roosevelt River, Southwestern Amazon basin

“…The Amazon River Basin contains the highest fish species diversity of any region on earth (Reis et al, 2003). The biodiversity results from processes operating at multiple spatial and temporal scales (Peláez & Pavanelli, 2018). Heterogenous environments can contribute to maintain biodiversity (Peláez et al, 2017).…”