Pollution tolerance, flight capacity and natural history explain metacommunity structure in high-altitude stream insects

Abstract

Aim: To test how different taxonomic and functional groups of aquatic insects from high-altitude streams respond to environmental and spatial gradients at multiple scales in Southeast of Brazil. Methods: Specimens were collected in 26 high-altitude streams distributed over a gradient of previously defined environmental quality. The taxonomic identification was made at the genus level and the functional classification was based on traits of flight capacity and pollution tolerance compiled from specific literature. We obtained local in situ data (limnological, sediments, and organic matter), as well as calculated land use at the riparian and drainage basin scale. A variation partitioning approach was used to explain species composition based on different response matrices deconstructed by both taxonomic groups and functional traits. The explanatory matrices encompassed environmental variables at three spatial scales and spatial variables extracted from Principal Components of Neighbor Matrices analysis. A linear model was applied to verify the possible correlation between spatial and environmental components. Results: The contribution of the spatial and environmental components varied strongly between taxonomic and functional groups. For taxonomic groups, the pure environmental component was more important for Odonata and Trichoptera, while spatial variables were more important for Diptera (non-Chironomidae) and Chironomidae, Coleoptera, Ephemeroptera, Plecoptera and Megaloptera. The sensitive groups with good flight capacity showed a greater environmental signature while the tolerant groups with low flight capacity had a greater spatial signature. Moreover, the important variables for explaining community variation were from different spatial scale (local, riparian and watershed) depending either on the analyzed taxonomic or on functional groups. However, a general effect of forests was found in several groups. Conclusions: It 2 Santos, M.R. et al. Acta Limnologica Brasiliensia, 2020, vol. 32, e20 to relate to both spatial and environmental factors concomitantly. In this sense, communities strongly affected by spatially structured environmental pressures would be expected to be strongly related to the spatial distance among sites as well. To disentangle the correlated effects of environmental and spatial variation on community composition, statistical techniques to partition the explained proportion of community variation were proposed (Borcard et al., 1992), becoming important tools in metacommunity studies. Moreover, the spatial scale used will be an important element to detect ecological patterns, both related to environmental and spatial factors (Leibold et al., 2004; Heino et al., 2017; Tonkin et al., 2017a). This premise is relevant mainly in continental aquatic environments in which many streams constitute networks (Frissell et al., 1986; Finn et al., 2011; Tonkin et al., 2017b) that behave like islands disconnected by the fragmented matrix (Bilton et al., 2001; Alemu et al., 2017; Tonkin et al., 2017a). The success of colonization and persistence of aquatic insects in