Congruence and responsiveness in the taxonomic compositions of Amazonian aquatic macroinvertebrate and fish assemblages

Abstract

Stream degradation in Amazonia is outpacing our ability to effectively monitor it for three key reasons: (1) Many changes are cumulative and occur gradually; (2) Scientists have failed to clearly link anthropogenic disturbances with ecological and economic indicators of concern to decision makers and the public; (3) There are too many potential indicators to assess in a cost-effective manner. Therefore, we sought to assess congruency at three taxonomic resolutions (species, genus and family) and between assemblages (fish species and macroinvertebrate genera) and groups of taxa (fish: Characiformes and Siluriformes; macroinvertebrates: Anisoptera, Heteroptera, Odonata, Trichoptera, Zygoptera, EPT [Ephemeroptera, Plecoptera and Trichoptera] and THZ [Trichoptera, Heteroptera and Zygoptera]). To do so, we assessed taxonomic, land-use and habitat data from 92 stream sites in the eastern Amazonian state of Pará. We found that anthropogenic disturbances of our sites influenced abundance and incidence of macroinvertebrate and fish taxa, but the two assemblages responded to slightly different stressors. Family and genera levels were suitable substitutes for similarity patterns measured at the macroinvertebrate genera and fish species levels, respectively. Odonata, Trichoptera, EPT and THZ were highly congruent with whole macroinvertebrate assemblage (genus level) variation. Characiformes was also congruent with whole fish assemblage (species level) variation. Congruence among macroinvertebrates and fish was intermediate (55% to 79%) and related to differing responses to environmental variables. Our results suggest that some groups (e.g., Odonata, Trichoptera and Characiformes) are useful surrogates of macroinvertebrate or fish assemblages to evaluate anthropogenic disturbance in Amazonian streams.