Composição e distribuição da fauna de Ephemeroptera (Insecta) em área de transição Cerrado-Amazônia, Brasil

Abstract

ABSTRACT. Composition and distribution of Ephemeroptera (Insecta) in Cerrado-Amazônia transition area, Brazil. The objective of this study was to respond if exist a pattern on the spatial distributions of Ephemeroptera nymphs in different streams and rivers from Suiá-Miçú Basin, MT, and how the streams are classifying according to the species composition. Were sample 12 streams and rivers, in three periods of the year. Were collected 1,356 individuals, distributed in seven families, 31 genus and 42 species and/or morphospecies. The most abundant locals were semi-lentics and with few shaded suggering that most light in the system offer, allochthonous material and autochthonous material like food resources. The greater estimates richness was found in lotic places, emphasizing that the Ephemeroptera presents greater richness in these places, once water current is essential for organic matter transporting. So much in the grouping analysis (TWINSPAM) as in the ordination (DCA) was observed the separation of lotic and semi-lentic environments as for species composition. It had a gradient in the composition similarity of lotic and small streams for lotic and big stream and for last, semilentics. The results of this study show that the physic structure of aquatic environments affect species composition. In that way, retreat of riparian vegetation and streams dam up can take significant losses in the diversity. KEYWORDS.Aquatic insects, Suiá-Miçú River Basin, lotic and semi-lentic environments, nymphs. RESUMO.O objetivo deste trabalho foi responder se existe padrão na distribuição espacial das ninfas de Ephemeroptera em diferentes córregos e rios da bacia do Rio Suiá-Miçú, MT, e como os córregos estudados estão classificados de acordo com a composição de espécies. Na coleta foram amostrados 12 córregos e rios, em três períodos do ano. Foram coletados 1356 indivíduos, distribuídos em sete famílias, 31 gêneros e 42 espécies e/ou morfoespécies. Os locais mais abundantes foram ambientes semi-lênticos, com pouco sombreamento no leito, sugerindo que a maior entrada de luz disporia, além do material alóctone, material autóctone como fonte de alimento. A maior riqueza de espécie e/ou morfoespécie, estimada, foi em ambientes lóticos enfatizando que os Ephemeroptera apresentam maior riqueza nestes locais uma vez que a correnteza é essencial para transportar a matéria orgânica particulada. Tanto na análise de agrupamento (TWINSPAM) como na ordenação (DCA) observou-se a separação entre ambientes lóticos e semi-lênticos quanto a composição de espécies. Percebeu-se um gradiente na similaridade de composição dos ambientes lóticos de pequeno porte para ambientes lóticos de grande porte e, por fim, os semi-lênticos. Os resultados deste estudo demonstram que a estrutura física dos ambientes aquáticos afeta a composição de espécies. Dessa forma, a retirada das matas ciliares e o represamento dos córregos podem levar à perdas significativas na diversidade. PALAVRAS-CHAVE.Insetos aquáticos, bacia do rio Suiá-Miçú, ambiente lótico e semi-lênt...

Environmental and spatial processes determining Ephemeroptera (Insecta) structures in tropical streams

“…The streams studied in the Cerrado region have their headwaters in steep areas at Serra do Roncador, are deeper and have a larger water flow Shimano et al, 2010). The speed of water flow is known to be one feature that causes variation in species composition of Ephemeroptera in the region (Shimano et al, 2010). Thus, variation in environmental structure can explain the observed differences in species composition showed by DCA in this study.…”

“…These models were based on the biology of the group. In this way, one model verified all parameters sampled, the second focused on the integrity of the streams (influence of integrity cited by Buss and Salles, 2007;Souza et al, 2010) and the third model emphasized the influence of the large streams (Vannote et al, 1980;Corigliano et al, 2001;Shimano et al, 2010).…”

“…Samples collected in the Corrente sub-basin, Cachoeirinha stream and Pindaı´ba river (Pindaı´ba The methodology used by Cabette et al (2010), DiasSilva et al (2010) and Shimano et al (2010) was used to collect Ephemeroptera nymphs. Fixed transects of 100 m were delineated and divided into 20 segments of 5 m. Samples were obtained through a sieve of 18 cm diameter and 0.05 mm mesh, and were collected three times per segment.…”

“…Amazonian streams are often structurally different, they originate usually in flat areas and are more susceptible to flooding than Cerrado streams, with less currents and more acidic waters. The streams studied in the Cerrado region have their headwaters in steep areas at Serra do Roncador, are deeper and have a larger water flow Shimano et al, 2010). The speed of water flow is known to be one feature that causes variation in species composition of Ephemeroptera in the region (Shimano et al, 2010).…”

“…The sensitivity of Ephemeroptera to physical, chemical and physical-chemical changes of an aquatic system has been well described in the literature (e.g., Brittain, 1982;Salles et al, 2004;Domı´nguez et al, 2006). Therefore, Ephemeroptera is regarded as a useful research subject in studies with different ecological approaches (e.g., Francischetti et al, 2004;Goulart and Callisto, 2005;Buss and Salles, 2007;Siegloch et al, 2008;Shimano et al, 2010;Souza et al, 2010). According to Brittain (1982), however, mayflies have limited longdistance dispersal abilities due to their fragile nature and short adult life span, which may effectively contribute to increasing the effect of space in community structuring.…”