Trait–environment relationships in Amazon stream fish assemblages

Abstract

Studies of trait–environment relationships provide important tools for the prediction of the response of biological communities to environmental alterations. The Amazon basin presents enormous potential for the development of research on this type of relationship, given the diversity of both its fish fauna and the aquatic ecosystems this fauna inhabits. The present study investigated the association between local environmental variables and the functional traits of fish in 54 streams of six major Amazonian basins. We identified the relationship between the characteristics of the streams (channel morphology, channel habitat units, riparian vegetation cover, large woody fragments and instream cover for aquatic organisms) and fish traits related to locomotion, habitat use and feeding behaviour. The fish fauna of the broader, deeper and more slowly flowing streams was dominated by nektobenthic species that exploit autochthonous resources such as fish and invertebrates. In narrow, fast‐flowing streams, by contrast, there was a predominance of benthic fishes with varying feeding habits, including periphytivorous and invertivorous species. Narrow, shady streams were inhabited by nektonic species adapted for the exploitation of resources from the marginal vegetation. The results of this study contribute to the understanding of the association between the functional structure of fish assemblages and local environmental variables in Amazonian streams. We hope that these findings will stimulate further research into the natural variation in stream fish assemblages that will ensure the development of more effective management strategies that better protect these important aquatic ecosystems.

Unravelling patterns of taxonomic and functional diversity of Amazon stream fish

“…The richness and abundance of small Neotropical catfishes and knifefish, for example, were much greater in streams rich in organic matter (Table S8), since they rely on this substrate for feeding (Brejão et al 2013). Our results agree with a study focusing on trait-environment relationships in the same stream sites (Santos et al 2019), which showed that a gradient from slower-flowing to faster-flowing waters was associated with changes in the type of substrates and in the ecomorphological patterns and taxonomic orders of fish communities.…”

“…These indices reflect the ecological significance of morphological attributes (Watson and Balon 1984). Details on morphological measurements are described in Santos et al (2019). We assigned species into seven trophic groups (Table S8) based on the literature.…”

“…Most available studies in the Amazon have focused on the role of local variables on stream fish taxonomic diversity (e. g. Mendonça et al 2005;Espírito-Santo et al 2009;Carvalho et al 2013), with little attention to the importance of large-scale variables. Even fewer studies have accounted for the responses of fish functional traits to environmental variables measured at multiple scales (Cilleros et al 2016;Santos et al 2019).…”

The effect of different logging regimes on the ecomorphological structure of stream fish assemblages in the Brazilian Amazon

“…To determine the ecomorphological traits of each fish species, we selected the five largest individuals that were of similar size to avoid the potential effects of ontogenetic variation in the morphological traits (Santos et al, 2019). For the species represented by fewer than five specimens, measurements were taken from additional specimens obtained from the ichthyological collection of the Goeldi Museum (Museu Paraense Emı´lio Goeldi; MPEG) in Belém.…”

Distance to large rivers affects fish diversity patterns in highly dynamic streams of Central Amazonia

“…In a functional perspective, the river-continuum hypothesis predicts that headwater systems should be primarily occupied by small-sized and nektonic fish species mainly dependent on allochthonous resources, while downstream systems should harbor larger species predominantly supported by autochthonous production, especially for benthic fish guilds [5,12,23]. However, increased connectivity with large rivers can reduce effects of local filters on assemblages and increase opportunities for opportunistic migration of species that typically do not reside in low-order stream, thereby increasing local functional richness [10,20].…”