Ephemeroptera, Plecoptera and Trichoptera assemblages from riffles in mountain streams of Central Brazil: environmental factors influencing the distribution and abundance of immatures

Abstract

The influence of environmental factors on the distribution of Ephemeroptera, Plecoptera and Trichoptera (EPT) immatures was investigated in streams of the Brazilian Center-West (Serra do Pireneus, Pirenópolis, State of Goiás). The insects were sampled by lifting the stones in front of a sieve (0.5 mm mesh) and then removing the insects from both the stone and the sieve. Sampling was carried out for 1 h at 5 collection sites over a period of 14 months. Air and water temperature (°C), water velocity (m/s), discharge (m 3 /s), electric conductivity (µS/cm), pH, and rainfall (mm) were also recorded. In general, we may state that altitude, hydrologic classification (order) and vegetation cover were the most important factors explaining the distribution of Ephemeroptera, Plecoptera and Trichoptera immatures. The influence of the rainfall on the temporal variation of the abundance of insects was stronger in stream segments of medium order (3 rd , 4 th order) compared to smaller streams (first order).Keywords: Ephemeroptera, Plecoptera, Trichoptera, lotic environments, larval distribution. RESUMO Comunidades de Ephemeroptera, Plecoptera e Trichoptera em riachos de montanha do Brasil Central: fatores ambientais influenciando a distribuição e abundânciaA influência de fatores ambientais sobre a distribuição de imaturos de Ephemeroptera, Plecoptera e Trichoptera (EPT) foi investigada em riachos do Centro Oeste Brasileiro (Serra do Pireneus, Pirenópolis, Estado de Goiás). Os insetos foram amostrados lavando pedras em frente a um rede (0,5 mm de malhas) e removendo os insetos tanto das pedras quanto das redes. A amostragem foi feita durante 1 h em cinco pontos de coleta em um período de 14 meses. Temperaturas do ar e da água (°C), velocidade da água (m/s), vazão (m 3 /s), condutividade elétrica (µS/cm), pH, e precipitação pluviométrica (mm) também foram registradas. Em geral, podemos afirmar que a altitude, a classificação hidrológica (ordem) e a cobertura vegetal foram os fatores mais importantes na distribuição de imaturos de Ephemeroptera, Plecoptera e Trichoptera. A influência da precipitação pluviométrica sobre a variação temporal da abundância foi maior em trechos de ordem média (3 a , 4 a ordem) quando comparado aos menores riachos (primeira ordem).Palavras-chave: Ephemeroptera, Plecoptera, Trichoptera, ambientes lóticos, distribuição larval. 612 BISPO, P. C. et al.

Diversity and structure of Ephemeroptera, Plecoptera and Trichoptera (Insecta) assemblages from riffles in mountain streams of Central Brazil

“…Nevertheless, in the rainy season, the value of the Shannon-Wiener index of station 3 (disturbed site) was similar to the value of station 5 (good environmental condition). In this case, the similar diversity between two stations with different environmental conditions in the rainy season could be explained by a possible redistribution of aquatic insects provoked by spates (BISPO et al 2006) that could disorder the spatial patterns of EPT distribution and diversity (BISPO & OLIVEIRA 1998, DINIZ-FILHO et al 1998. Station 4, located in Pirenópolis town, the site with the greatest anthropic action, had smaller values of richness and of diversity.…”

“…According to DCA I, the scores representative of the samples collected in 1 st order streams tended to have greater values than those of samples collected in sites of 3 rd and 4 th orders. Therefore, stream size and factors related to it were important for structuring the EPT fauna (BISPO et al 2006). It is important to highlight that subjacent to variation in stream size are the changes in the predominant inputs of energy, the daily variation of temperature and hydraulics (VANNOTE et al 1980, STATZNER & HIGLER 1986.…”

“…This pattern could be explained by the high environmental seasonality of the cerrado biome, that is, the seasonal variability can conceal the effect of spatial variability on the faunal structure. The exception was station 1, whose samples, collected in different periods of the year, formed a group; this pattern, according to BISPO et al (2006), was mainly due to the presence of taxa characteristic of higher altitudes that made up a distinctive fauna. In a general manner, from the spatial point of view, data of the present work showed that anthropic influence determined the patterns of diversity while the size of streams (1 st and 3 rd -4 th orders) determined the faunistic composition.…”

“…1980, RICHARDS et al 1993, ZAMORA-MUÑOZ et al 1993, ZAMORA-MUÑOZ & ALBA TERCEDOR 1996, BISPO et al 2006. Those characteristics vary in time and space; therefore, it is expected that those variation determine the spatial and temporal alteration of diversity and of structure of fauna in the aquatic communities.…”

“…According to MARCHANT et al (1995), patterns found for EPT represent the same patterns found for the macroinvertebrate fauna as a whole; for this reason, studies could be restricted to that fauna. BISPO et al (2006) have investigated the effect of environmental factors over the distribution of EPT and have concluded that precipitation, stream order and altitude were the main factors that determine distribution and fauna abundance. The present work aimed to evaluate the effect of spatial variation, including the effects of stream size, anthropic action, and seasonality (dry and rainy seasons) over diversity and structure of Ephemeroptera, Plecoptera and Trichoptera assemblages.…”