Effects of riparian vegetation width and substrate type on riffle beetle community structure

Abstract

Riffle beetle community structure is influenced by the preservation condition of stream riparian vegetation. Though, the width of riparian vegetation required to ensure conservation of stream insect communities is still controversial. Effects of alterations in riparian vegetation widths on stream insect community structure can be overcame by other environmental variables, like substrate type, hindering accurate assessments. We tested the effects of different riparian vegetation widths (>40, 30–15, 15–5 and <5 m) along with different substrate types (inorganic and organic) on riffle beetle community structure in southern Brazilian 4th‐ to 5th‐order streams. Riparian buffer widths and substrate types influenced riffle beetle community structure, but no interaction between them was observed. Reduced riparian vegetation widths downstream were associated with changes in riffle beetle dominant genera (Macrelmis predominated only in streams with narrowest riparian widths). Additionally, communities in organic substrates had lower equitability and different dominant genera (Hexacylloepus and Heterelmis) than inorganic ones. Our results showed that reductions in riparian vegetation were associated with water pollution and changes in riffle beetle community structure, suggesting that buffer strips narrower than 5 m are not adequate to maintain environmental integrity of southern Brazilian streams. These results have special importance for the conservation of stream insects in Brazil, as reductions up to less than 5 m in stream banks of small properties are allowed by the new Brazilian Forest Code, independently of stream order.

Potential distribution of riffle beetles (Coleoptera: Elmidae) in southern Brazil

“…Montane regions with higher declivity, in turn, promote water oxygenation, an important environmental driver of Elmidae assemblages at local spatial scales (Braun et al 2014a). In this context, previous studies showed that the deforestation and conversion of the riparian vegetation were associated to changes in the composition of subtropical Elmidae assemblages in Brazil (Braun et al 2018a(Braun et al , 2018b, possibly because these alterations affected the quality of the allochthonous material entering the streams. Forest cover was also an important predictor of richness of Elmidae taxa.…”

“…The role of ecoregions in explaining large-scale diversity patterns of freshwater species was first proposed by Abell et al (2008), mainly based on the distribution of fish species. Elmidae assemblage composition varies across different Brazilian regions, as shown by many studies (Passos et al 2010;Segura et al 2013;Braun et al 2018b). Elmidae assemblage composition varies across different Brazilian regions, as shown by many studies (Passos et al 2010;Segura et al 2013;Braun et al 2018b).…”

“…Forested biomes elsewhere in Brazil have displayed high elevated richness of Elmidae, such as the Amazon Rainforest and Atlantic Forest (Jäch & Balke 2008). This region has been shown to have higher diversity of genera of Elmidae (Braun et al 2018b) and other stream insects compared to other subtropical and tropical regions of Brazil ). This region has been shown to have higher diversity of genera of Elmidae (Braun et al 2018b) and other stream insects compared to other subtropical and tropical regions of Brazil ).…”

“…In fact, the community structure and the occurrence of many genera are influenced by the presence of native vegetation, water temperature and oxygen content values (Passos et al 2003a,b;Braun et al 2014aBraun et al ,b, 2018a. stream and basin level) show that the spatial distribution of Elmidae assemblages is influenced by environmental factors such as elevation, substrate type (organic and inorganic substrates) and riparian vegetation structure (Passos et al 2003a,b;Elliott 2008;Jäch & Balke 2008;Braun et al 2014bBraun et al , 2018b. stream and basin level) show that the spatial distribution of Elmidae assemblages is influenced by environmental factors such as elevation, substrate type (organic and inorganic substrates) and riparian vegetation structure (Passos et al 2003a,b;Elliott 2008;Jäch & Balke 2008;Braun et al 2014bBraun et al , 2018b.…”

“…Considering the importance of local and regional environmental factors for the spatial distribution of riffle beetles (Passos et al 2003a(Passos et al , 2003bSite et al 2003;Elliott 2008;Jäch & Balke 2008;Braun et al 2014bBraun et al , 2018b, we modelled their potential distribution in relation to large-scale climatic and landscape environmental factors (topography, hydrological variables and land cover). Considering the importance of local and regional environmental factors for the spatial distribution of riffle beetles (Passos et al 2003a(Passos et al , 2003bSite et al 2003;Elliott 2008;Jäch & Balke 2008;Braun et al 2014bBraun et al , 2018b, we modelled their potential distribution in relation to large-scale climatic and landscape environmental factors (topography, hydrological variables and land cover).…”