Effects of Local Environmental and Landscape Variables on the Taxonomic and Trophic Composition of Aquatic Insects in a Rare Forest Formation of the Brazilian Amazon

Abstract

In the present study, we analyzed a unique phytophysiognomy in the Amazon region, which is formed by savanna-like vegetation on iron-rich soil (known locally as canga) located within an iron-ore mining region. We used the habitat template theory to test the hypothesis that changes in the physical-chemical properties of streams and the physical structure of their habitats at in-stream and micro-basin (landscape) levels affect the taxonomic and trophic composition of immature aquatic insects. For this, we used a local environmental matrix composed of nine physical-chemical and structural habitat variables, together with the Habitat Integrity Index. We also calculated landscape metrics based on the area of the microbasin, such as relief, slope, mean current flow, and vegetation cover. We divided the aquatic insects into five functional feeding groups based on their diet and food sources. Our results indicate that changes in the trophic level of the insects of the orders Ephemeroptera, Plecoptera, and Trichoptera are more easily observed than the taxonomic structure of communities. The loss of environmental integrity and vegetation cover were responsible for 84% of the variation observed in the composition of functional feeding groups (FFGs). Our study shows that aquatic insect communities in the canga and in the Amazon regions dominated by forest require specific in-stream and landscape conditions. These findings reinforce the need for the preservation of areas of canga vegetation, which not only have a unique levels of biological diversity, but are also targeted for the exploitation of their economically valuable natural resources.

Benthic Macroinvertebrates Associated with Riparian Habitat Structural Diversity in an Eastern Amazon Stream Urbanization Gradient

“…Better conserved riparian vegetation along the Cereja River, measured by the RHDI, is associated with greater macroinvertebrate diversity, especially of Ephemeroptera and Trichoptera, which were greatly reduced in abundance and diversity in altered areas, and absent from impacted areas, partly supporting our first hypothesis. Plecoptera were not found and have low diversity in tropical streams (de Paiva et al, 2017;Luiza-Andrade et al, 2020). In contrast to our predictions, higher Chironomidae and Coleoptera abundance were associated with high RHDI scores in natural areas.…”

Linnean and Wallacean shortfalls of Leptophlebiidae (Ephemeroptera: Insecta) in the Brazilian Amazon

“…Some genera, like Leentvaaria Demoulin, 1966, Terpides Demoulin, 1966 and Thraulodes Ulmer, 1920, have been mentioned in previous studies up to the genus level in the nymphal phase (Luiza‐Andrade et al, 2020, 2022). However, there is no formal record of any species for Pará State, revealing fragmented knowledge about species in these genera.…”

Environmental variables affect the diversity of adult damselflies (Odonata: Zygoptera) in western Amazonia

“…This region has a humid tropical climate with dry winters, classified as AWi in the Köppen system (Peel et al, 2007). More than 95% of this conservation unit is covered by dense hardwood forests, with the remaining area consisting of a type of savanna, known locally as the "canga", which grows on soils rich in iron-ore, and is referred to as the Iron Triangle (Ab 'Saber, 1986;Luiza-Andrade et al, 2020). The rainy season lasts from November to May, and the dry season, from June to October, with total annual precipitation of 1800-2300 mm (Moraes et al, 2005).…”

“…The streams in the Itacaiúnas watershed have white (milky coffee-colored) water during the dry season, changing to yellow or red in the rainy season, when the sediment load increases (Ruivo & Sales, 1989). Iron ore has been extracted within this area since 1970, which prompted the creation of the National Forest (IBAMA, 2003;Luiza-Andrade et al, 2020). As a result, the companies operating within this area must strictly respect Brazilian environmental legislation (the forest code, federal law 12,561/2012), which mandates the preservation of a 30-m buffer of riparian vegetation around all streams (ITV, 2017).…”

“…In the Amazon rainforest, the principal impacts on stream systems are derived from human activities, in particular, cash cropping (Cunha et al, 2015), cattle ranching, logging (Calvão et al, 2016), hydroelectric dams, and mining (Monteiro, 2005;Fearnside, 2006;Luiza-Andrade et al, 2020), all of which may influence the physical structure of the stream margins and the quality of the water, which affect the stability of the environmental (Nessimian et al, 2008;Brasil et al, 2014a;Cunha et al, 2015;Oliveira Júnior et al, 2015). Mining is widespread in the Amazon region, and can have a significant impact on many of the natural characteristics of the stream systems (Callisto et al, 1998).…”