Habitat loss caused by changes in land cover and use is considered one of the main causes of biodiversity decline (Kim et al., 2015; Millennium Ecosystem Assessment, 2005; Pimm et al., 2014). This change in land cover and use is a way to meet the demand for food and generally affects large areas, causing the complete replacement of native forest by cultivated areas (Tilman et al., 2001). Thus, the increase in human population and consumption directly contributes to the expansion of agricultural areas and the decline of biological diversity (Wilting et al., 2017).
Terrestrial environments are increasingly experiencing the negative effects caused by different types of land use (Cajaiba et al., 2018; Dos Santos et al., 2016). Similar effects of loss of diversity were also observed in aquatic environments (Vieira et al., 2020), since these environments have a strong relationship with the terrestrial environment (Pusey & Arthington, 2003). Thus, changes in the terrestrial landscape also alter the aquatic environments, compromising the maintenance of biodiversity and ways of life of local populations (Dudgeon, 2019).
The transition area between Cerrado-Amazon biomes has been heavily impacted in recent years, it is located in the arc of Amazonian deforestation, responsible for the highest rate of deforestation in the Amazon with 500,000 km2 of deforested area (IPAM, 2015). As a result, the region suffers from changes in the soil, climate change and loss of biodiversity, making it urgent to monitor the region's fauna.
To protect stream assemblages and minimize loss of diversity, prior knowledge of biodiversity is important, reducing the Linnean gap, as only by knowing the biological components is it possible to develop management actions, aiming to recover, conserve or preserve its integrity (Lawton et al. al., 1998). However, surveying all species requires time and financial resources, making the task unattainable in the short term (Lawton et al., 1998; Margules & Pressey, 2000).
A solution to the lack of information about species and the difficulty of assessing and monitoring biodiversity is the monitoring of a surrogate group (Heino et al., 2003; Landeiro et al., 2012; Lindenmayer et al., 2015), a taxonomic group that presents congruence, similarity in terms of distribution and response to changes in the environmental gradient with other groups (Bini et al., 2007; Paavola et al., 2003; Paszkowski & Tonn, 2000). Congruence is generally higher between phylogenetically and ecologically related groups (Bastos et al., 2021; Gaston, 1996). When congruence is evidenced, the response patterns obtained for a biological group can be extrapolated to others in the same geographic area (Heino & Mikra, 2006), thus reducing time and expense to develop conservation actions (Howard et al., 1998; Trindade-Filho & Loyola, 2011).
For a more adequate assessment of lotic ecosystems, the European Union’s Water Framework Directive suggests the assessment of multiple sets (macrophytes, algae, macroinvertebrates and fish), but most aquatic biomonitoring programs evaluate only one of the groups (fish and macroinventebrates are the more common) (Feio et al., 2021; Ruaro et al., 2020). Both groups are sensitive to anthropic disturbances, macroinvertebrates to loss of riparian forest (Dala-Corte et al., 2020; Martins et al., 2021; Valente-Neto et al., 2021), while fish to fragmentation of migratory corridors and hydromorphological changes (Leitão et al., 2018; Schinegger et al., 2016). One advantage of using fish in biomonitoring is the high taxonomic knowledge and characteristics of the species, on the other hand macroinvertebrates are less taxonomically known, however coarser levels of identification are sufficient for rigorous bioassessments (Silva et al., 2017; Whittier & Van Sickle, 2010).
In this study we used fish assemblages, Heteroptera and Odonata to evaluate the response of groups that occupy different pools within the aquatic habitat (inside, surface and around the water), they are considered excellent indicators of the conditions found in aquatic environments, they represent different trophic levels, providing a complete view of the aquatic environment (Lyons et al., 1995; Rosenberg & Resh, 1993), as well as good models to assess environmental impacts (Dias-Silva et al., 2010; Juen et al., 2007; Wittwer et al. al., 2010), as they require specific habitats, being vulnerable to the loss of physical integrity of aquatic systems (Giehl et al., 2014; Miguel et al., 2017). In the order Odonata, the suborders Zygoptera and Anisoptera respond oppositely to the environmental condition, resulting in a mixed response of Odonata as a whole. One way around this situation is to analyze the suborders separately (Oliveira-Junior et al., 2015, 2017).
Our objective was to evaluate the congruence between fish assemblages, Heteroptera, Odonata (Anisoptera and Zygoptera) in streams in the Amazon-Cerrado transition area and identify the relationship between the studied assemblages and environmental conditions. To achieve this goal, we answered the following questions: What is the congruence between Heteroptera and Odonata fish groups (Anisoptera and Zygoptera) in Amazon-Cerrado transition streams under different environmental conditions? And what environmental variables or spatial filters affect the distribution of these assemblages? Our hypothesis is that (i) Heteroptera and Odonata (Anisoptera and Zygoptera) will show strong congruence, as they are phylogenetically and ecologically close groups; as related groups respond similarly, they will soon show a similar response to the environmental gradient (Gaston, 1996); (ii) Heteroptera will respond to environmental variables, showing greater diversity when there is greater integrity, and to space; as they inhabit the water surface and require the environmental integrity of streams (Benstead & Pringle, 2004; Schuh & Slater, 1995).