Abstract
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.
Highlights
Riparian vegetation is important for the maintenance and regulation of the aquatic environment (Gonçalves Júnior et al, 2014), serving as a barrier to sediment supply and maintaining biological conditions
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
This study had an exploratory character and we tried to answer the following question: how does the environmental variation generated by changes in land uses affect the alpha and beta components of the diversity of Trichoptera assemblages in streams? our objectives were: (i) to determine the diversity of Trichoptera in streams surrounded by riparian vegetation and agriculture; (ii) to determine the effects of environmental variables and geographical position on Trichoptera assemblages in natural and rural streams; and (iii) to determine the contribution of the alpha and beta components to the regional diversity of Trichoptera in the studied area
Summary
Riparian vegetation is important for the maintenance and regulation of the aquatic environment (Gonçalves Júnior et al, 2014), serving as a barrier to sediment supply and maintaining biological conditions. Shading provided by riparian vegetation assists in controlling the temperature of the streams and increases the environmental complexity and availability of food (Naiman et al, 2010). Riparian vegetation provides corridors for wildlife movement, which increases biodiversity on a spatial scale and contributes to the maintenance of water quality (Naiman et al, 2010). Reducing riparian vegetation increase the temperature, nutrient concentration and sediment content within streams, which damages the ecological integrity of the aquatic ecosystem (Blevins et al, 2013). Any changes generated by agriculture alter the physical and chemical structure of the streams, which can modify the composition of aquatic communities by taxa replacement (turnover) or changes in taxonomic richness, occurring gain and loss of taxa (nestedness) (Hepp & Santos, 2009; Hepp et al, 2010; Fugère et al, 2016)
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