Alpha and beta diversities of Trichoptera (Insecta) assemblages in natural and rural subtropical streams

Abstract

Aim The aim of this study was to determine the diversity of Trichoptera in subtropical streams and the effects of environmental variables and geographical position on alpha and beta diversity in natural and rural streams. Methods We collected Trichoptera with a Surber sampler in 12 small order subtropical streams (six streams with apparent absence of anthropic disturbance and six streams with rural activity in their drainage areas) and measured limnological variables. We evaluated the effects of environmental variability and geographical distance on the dissimilarity of the assemblage and calculated the contribution of alpha and beta diversity for each stream. Results We collected a total of 1,264 Trichoptera larvae distributed in 17 genera and 11 families. The genera Phylloicus and Smicridea were found in almost all streams. We observed a positive effect of environmental variability on biological variability but not of geographical distance. The environmental variability was basically generated by the influence of higher concentrations of dissolved organic carbon and nutrients. We observed the greatest contribution of the alpha diversity of the Trichoptera assemblages in natural streams and of beta diversity in the rural streams. Conclusions Our results demonstrate that the variability of Trichoptera is affected by environmental characteristics, but not by geographical position.

Agriculture affects functional diversity of aquatic insects in Subtropical Atlantic Forest streams

“…Studies demonstrate that changes in areas adjacent to streams can cause chemical changes in the water (for example, through the transport of sediments or chemicals) favoring the dominance of tolerant organisms (Hepp et al, 2010;Huiñocana et al, 2020;Hepp et al, 2021). Among the Trichoptera genera, Smicridea and Itaura are widely observed in streams with agricultural use (Breda et al, 2020), while Caenis has been reported as an Ephemeroptera genus tolerant to anthropogenic disturbances (Arimoro & Muller, 2010). In addition, our results clearly demonstrated the effects of organism abundance on richness.…”

“…Thus, we can see that changes in streams adjacent areas (e.g., land use) are important environmental predictors in the structuring of aquatic insect communities. Thus, it is expected that changes in land use in the stream drainage area will affect the limnological water quality and, consequently, the aquatic biota (Breda et al, 2020;Castro et al, 2021). In this study, we observed that the vegetation removal was decisive for the change in limnological variables such as water temperature, pH, and dissolved oxygen.…”