Disentangling spatial and environmental determinants of fish species richness and assemblage structure in Neotropical rainforest streams

Abstract

Freshwater ecology templates were developed in temperate streams, but whether they also apply to tropical streams that harbour a higher biological diversity than their temperate counterparts remains uncertain. This is particularly true for tropical fish assemblages inhabiting small streams that have been less studied than larger, higher‐order lowland streams. Here, we disentangled the strength of spatial (longitudinal and environmental) drivers, and scale‐specific (drainage basin, reach and local scale) determinants of species richness and composition of freshwater fish assemblages inhabiting small streams in French Guiana. We found that species richness increased from upstream to downstream but also with increasing local habitat structural diversity independently of stream position in the upstream–downstream gradient. This pattern was shared by the two most speciose fish orders (Characiformes and Siluriformes), demonstrating that species addition rather than species replacement shaped species richness in these assemblages. Species composition of fish assemblages was determined equally by their spatial structure within drainage and by the environment, and assemblages differed both with distance and along an upstream–downstream gradient. The environmental effect on species assemblages indicated by the fact that almost all environmental descriptors had slight but nonetheless significant effects on assemblage composition, probably reflecting species‐specific responses to the local environment. In contrast, despite a strong micro‐endemism between drainages for some taxa, assemblages were only slightly affected by river drainage identity, since widespread species were a common constituent of assemblages in all rivers. We identified five species assemblages characterising different local habitat features from torrential areas to lowland muddy areas. We also distinguished fish assemblages from confluence areas with larger rivers, which differed from the other five assemblages. The fish zonation patterns we report can constitute a benchmark for future studies measuring the impact of anthropogenic disturbances on Neotropical forest streams.

Biogeographic freshwater fish pattern legacy revealed despite rapid socio‐economic changes in China

“…Efforts have increasingly been made to distinguish natural and human drivers that structure fish assemblages (Brucet et al, ; Cilleros, Allard, Vigouroux, & Brosse, ; Henriques et al, ). However, due to a scale‐dependent effect (Menegotto, Dambros, & Netto, ), there is still no consensus on the main drivers that affect fish diversity and assemblage composition.…”

“…Efforts have increasingly been made to distinguish natural and human drivers that structure fish assemblages (Brucet et al, 2013;Cilleros, Allard, Vigouroux, & Brosse, 2017;Henriques et al, 2017).…”

Environmental and spatial effects on coastal stream fishes in the Atlantic rain forest

“…Studies of small, non‐impacted tropical streams are still scarce ( e.g. , Cilleros, Allard, Vigouroux, & Brosse, ) probably due to the difficulty of accessing these environments, and their increasing scarcity due to human impacts. The objective of this study is to characterize the factors that seem to govern fish assemblage structure in non‐impacted Atlantic Forest coastal streams.…”

Fish taxonomic and functional diversity in mesohabitats of the River Kakada, Caura National Park, Venezuela

“…Contrastingly, the larger functional spaces were observed in the mesohabitats with presence of riparian forest. The structural complexity of the mesohabitats in rivers of the Guiana Shield favours the coexistence of a high diversity of fishes, as a result of a wider variety of trophic resources (Cilleros et al, 2017), which might enable the coexistence of species with different traits to exploit specific resources such as periphyton and benthic macroinvertebrates, and that are adapted to specific microhabitats. However, the functional richness was not higher than randomly expected in these mesohabitats.…”

“…Fish assemblages in forested rivers of the Guiana Shield sustain a high diversity of species, in spite of their sometimes high acidity. In these rivers, the fish taxonomic diversity is influenced by an altitudinal gradient, the current velocity and the substrate type (Cilleros et al, 2017). For instance, at the segment scale, represented by a sequence of pools and rapids, these rivers show a higher fish diversity in mesohabitats where the accumulation of de-tritus and leaf litter is high and with high structural complexity (Machado-Allison et al, 2003), and the species show associations to distinct mesohabitats according to substrate type, the presence of aquatic vegetation and the structure of the riparian forest (Chernoff et al, 2003).…”