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.

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Revista Brasileira de Zoologia 24 (2): 283-293, junho 2007The structure of the fauna of aquatic insects in lotic environments is directly related to geomorphology, hydrology, quality of water, quality and availability of food resources, dominant substratum, temperature and dissolved oxygen (VANNOTE et al. 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.Among the aquatic insects, Ephemeroptera, Plecoptera and Trichoptera, usually known as EPT, comprise a rich assemblage of taxa in low and medium order cobble streams. These organisms are sensitive to environmental perturbations and occur, mainly, in clean and well-oxygenated waters. Due to those characteristics, these organisms are frequently considered as good indicators of water quality (ROSENBERG & RESH 1993). 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. Caixa Postal 131, Goiás, ABSTRACT. The diversity and structure of Ephemeroptera, Plecoptera and Trichoptera (EPT) assemblages in streams of Central Brazil (Serra dos Pireneus, Pirenópolis, State of Goiás) was investigated. Abundance data of EPT were obtained in Central-West Brazilian streams in order to evaluate the effect of spatial variability, including the effect of size of the stream and anthropic action, and seasonality (dry and rainy seasons) on faunal diversity and structure. The immatures were collected with circular sieves (0.5 mm mesh) during one hour at five collection stations over 14 months. From a spatial point of view, the data showed that anthropic action determined the patterns of diversity whereas the size of streams (1 st and 3 rd -4 th orders) determined the faunistic composition. In addition, environmental seasonality was an important factor for structuring the EPT fauna. Div

Alpha, beta and gamma are three components of species diversity. Knowing these attributes in floodplain lake phytoplankton communities is vital when selecting conservation areas. Species diversity is commonly used with other taxonomic groups, but rarely with phytoplankton. We compared the number of phytoplankton species (alpha diversity) from 21 Middle Araguaia River floodplain lakes in the 2000 and 2001 rainy and dry seasons. From these samples we estimated complete survey species richness (gamma diversity), quantified differences in species composition between lakes (beta diversity) and assessed the influence of abiotic variables on beta diversity. We recorded a total of 577 taxa. The Sjack1 estimator indicated that 62.31% of taxa were sampled in the 2000 rainy and 67.65% dry seasons, and 68.36% in the 2001 rainy and 73.5% dry seasons. In almost all seasons, alpha diversity negatively correlated with latitude. Beta diversity (b-1) was higher in high water periods, especially in 2000. This may have been caused by isolated heavy rainfall, which would have increased environmental heterogeneity and raised beta diversity. DCA showed differences in phytoplankton composition between rainy and dry seasons in 2000 and 2001, reflecting the influence of flood pulses on phytoplankton composition. The Mantel test indicated spatial distribution patterns where geographically more distant lakes had less-similar phytoplankton communities.

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