Taxonomic richness of fish, arthropod, and macrophyte
assemblages
We sampled fish, arthropod and macrophyte assemblages at each stream
site. Those three assemblages were selected because they represent
diverse biotic components of stream communities, and are associated with
key ecosystem processes, such as standing biomass (Moi et al., 2021).
All fish were identified to species; arthropods and macrophytes were
identified to species or genus. We recorded 141 fish species, 321
arthropod taxa, and 43 macrophyte taxa across the two study areas.
Importantly, taxonomic richness of the assemblages did not differ
markedly between Amazonia and Uruguay stream sites (see, Figure 1d).
However, to account for possible differences in population densities and
sampling effort among sites, we estimated taxonomic richness as the Chao
index with abundance-based data using the R package iNEXT (Hsieh et al.,
2016). The Chao index is based on rarefaction and extrapolation of Hill
numbers. It provides an unbiased estimate of asymptotic taxonomic
richness, thus enabling comparisons among areas with different potential
levels of assemblage richness.