Composition and diversity of Trichoptera (Insecta) larvae communities in the middle section of the Jacuí river and some tributaries, State of Rio Grande do Sul, Brazil

Abstract

The taxonomic composition and diversity of Trichoptera larvae communities were studied in four lotic sites in central region of State of Rio Grande do Sul. Sampling was done monthly from June, 2001 to May, 2002 in four sites located at the middle section of Jacuí River (Point 4) and in three tributaries (Carijinho River - Point 1; Lajeado da Gringa - Point 2 and Lajeado do Gringo - Point 3), with a Surber sampler. The total number of larvae collected was 29,143, belonging to 25 genera distributed in nine families; twenty of these genera are new records for the State. The highest abundance was found at Point 2 (n = 12,547). The highest standardized richness, for a 1,177 specimens sample chosen by chance, was recorded at Point 1, followed by Point 4 (17.7 and 16 genera, respectively). The highest diversity was found at Point 1, and the lowest at Point 3 (H' = 1.31 and H' = 0.77, respectively). Point 1 had the lowest anthropic influence and the best preserved riparian vegetation, while Point 3 presented the highest anthropic impact, and a very reduced riparian vegetation. The diversity of Trichoptera observed in this study is low, compared to the estimated maximum theoretical diversity. Low diversity values are related to the low evenness, since the richness was relatively high. The Trichoptera larvae communities seem to be related to the food availability and physical features (riparian vegetation and anthropic influence) of the study sites.

Diversity and distribution of riffle beetle assemblages (Coleoptera, Elmidae) in montane rivers of Southern Brazil

“…Site 4 is of 7 th order, and had the lowest DO and WC mean values, accounting for the lowest richness and abundance. However, the strong water level fluctuation determined by the operation of the Hydroelectric Power Station Dona Francisca (only 2 km upstream), as well as the absence of riparian vegetation and of Podostemum (Spies et al 2006, Floss et al 2012, are possibly the most important factors avoiding the Elmidae assemblages establishment.…”

“…Rivers are of 1 st to 7 th order, according to Strahler (1952) classification, and their beds are constituted mainly by gravels, cobbles and boulders (Neri et al 2005). Aquatic vegetation is scarce, but Podostemum can be common in certain stretches (Spies et al 2006, Floss et al 2012. Lentic environments are rare, represented by few backwaters located near the beginning of the lower Jacuí (Spies et al 2006).…”

“…Aquatic vegetation is scarce, but Podostemum can be common in certain stretches (Spies et al 2006, Floss et al 2012. Lentic environments are rare, represented by few backwaters located near the beginning of the lower Jacuí (Spies et al 2006).…”

“…Previous studies show that this region contains a very diversified macroinvertebrate assemblage (Neri et al 2005, Spies et al 2006, Siegloch et al 2008, Floss et al 2012, due to its location in a transitional relief area, and also to the occurrence of the incrusting aquatic macrophyte Podostemum A. Michaux, 1803 (Floss et al 2012). Besides, the middle Jacuí course has part of its marginal areas protected by a state park, Parque Estadual da Quarta Colô nia (PEQC).…”

Trichoptera as bioindicators of habitat integrity in the Pindaíba river basin, Mato Grosso (Central Brazil)

“…Trichopterans are very sensitive to changes in physical and chemical structure of aquatic environments (Spies et al, 2006), anthropogenic alteration and variation in canopy cover. Accordingly, these are also the main variables affecting its distribution in the Cerrado (Oliveira and Froehlich, 1997).…”