No abstract

Community assembly theory is founded on the premise that the relative importance of local environmental processes and dispersal shapes the compositional structure of metacommunities. The species sorting model predicts that assemblages are dominated by the environmental filtering of species that are readily able to disperse to suitable sites. We propose an ecophysiological hypothesis (EH) for the mechanism underlying the organization of species-sorting odonate metacommunities based on the interplay of thermoregulation, body size and the degree of sunlight availability in small-to-medium tropical streams. Due to thermoregulatory restrictions, the EH predicts (i) that larger species are disfavored in small streams and (ii) that streams exhibit a nested compositional pattern characterized by species’ size distribution. To test the EH, we evaluate the longitudinal distribution of adult Odonata at 19 sites in 1st- to 6th-order streams in the Tropical Cerrado of Brazil. With increasing channel width, the total abundance and species richness of Anisoptera increased, while the abundance of Zygoptera decreased. The first axis of an ordination analysis of the species abundance data was directly related to channel width. Mean and maximum thorax size are positively correlated to channel width, but no relationship was found for the minimum thorax size, suggesting that there is no lower size constraint on the occurrence of these species. Additionally, a nested compositional pattern related to body size was observed. Our results support the EH and its use as an ecological assembly rule based on abiotic factors. Forest cover functions as a filter to determine which species successfully colonize a given site within a metacommunity. As a consequence, the EH also indicates higher treats for small-bodied zygopterans in relation to the loss of riparian forests in tropical streams.

A retirada ou a substituição da vegetação ripária provoca uma alteração no ambiente físico, no fluxo sazonal e na qualidade química da água. Essas modificações podem causar a diminuição da riqueza pela extinção local de espécies. O objetivo deste trabalho foi avaliar o efeito do distúrbio da integridade ambiental sobre a riqueza e composição de espécies de Odonata adultos em córregos com diferentes níveis de conservação, na Bacia do Rio Suiá-Missu, Mato Grosso, Brasil. As modificações nos sistemas aquáticos afetaram a comunidade de Odonata, provavelmente devido às exigências ecofisiológicas e comportamentais relacionadas a adultos e larvas. Anisoptera, que necessitam de ambientes com maior incidência de sol devido ao tamanho do corpo, apresentaram maior riqueza de espécies em ambientes com menor cobertura vegetal. Por outro lado, os Zygoptera geralmente habitam riachos com cobertura vegetal mais densa, e por isso, apresentaram um decréscimo de sua riqueza em locais alterados, devido à maior entrada de luz e/ou variação do calor. Assim, para as duas subordens, as alterações ambientais não precisam ser severas para produzir modificações significativas na composição, indicando que os serviços ecossistêmicos poderiam ser perdidos, mesmo com alterações parciais do meio físico. PALAVRAS-CHAVE: ambientes aquáticos; biodiversidade; integridade ambiental; libélulas. Composition and richness of Odonata (Insecta) in streams with different levels of conservation in a Cerrado-Amazonian Forest ecotone ABSTRACTThe removal or substitution of riparian vegetation causes disturbance in physical environment, seasonal water flow and water chemical quality. These modifications can cause decrease in species richness by local extinctions. The aim of this study was to examine the effect of disturbance in the physical environmental on the richness and species composition of Odonata adults in streams with different levels of conservation in the river Suiá-Missu basin, Mato Grosso, Brazil. Modifications in the aquatic systems affected the Odonata community, probably because their ecophysiological and behavioral requirements of adults and larvae. Anisoptera species, which require sunny environments because of their body size, had higher species richness in environments with low plant cover. On the other hand, Zygoptera species, which generally inhabit streams with dense vegetation, presented a decrease in richness in disturbed environments, as a result high sunlight radiation and/or variations in temperature. Hence, in both suborders, environmental perturbations do not need to be severe to change species composition, indicating that ecosystem services could be lost, even with only partial alterations in physical environment.

Structural properties of aquatic habitats are the basis of several theories produced to explain the functioning of aquatic environments. We predicted a longitudinal change of ecosystem properties along the river, and also that potamal areas of the river are similar to lakes. In rivers with periodic floods we also expect a high degree of similarity due to increased environmental similarity and increase dispersal of component species. Otherwise, rivers must be conceived as a landscape element with an intrinsic hierarchical nature and dispersal among its parts are constrained by this structure. Under this view, we also could expect that different basin or different ''micro-basin'' could present communities that are historically different in their general properties. Here, we aimed to describe odonate larval communities in the Pantanal Mortes-Araguaia river basin in Brazil comparing the composition, species richness and community structure between lakes and rivers, and also the possible differences among river basins. The field work was done in three rivers and three lakes chosen to conform to a paired experiment, each pair in a different river basin. An aggregated sampling unit was used based on Ekman dredge and D-nets replicated on each site. We sampled 936 individuals distributed in 30 genera and a total of 34 morphotypes. There was no difference in species richness among lakes and rivers, but a marked difference among basins. Samples from the same basin present a higher similarity of the species abundance relations than among river or lake samples. We also did not observed differences in composition and community structure between large rivers and lakes, in the same basin. The results supported the concept of structural similarity between large rivers and lakes and the differences observed among basins could indicate historical events in colonization that are shaping communities characteristics.

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...

-Community diversity is expected to reflect variations in local conditions but, recently, ecologists have started to realize that local diversity is also under pressure from global processes. As a result, the traditional view of community structure based on local interspecific interactions was replaced by the idea that community structure is a result of multiple processes acting in different spatial scales. This study is aimed at quantifying the relative importance of spatial, environmental and spatially structured processes on Ephemeroptera community in Cerrado streams in Brazil. Thirty-four rivers and streams in the Brazilian state Mato Grosso were sampled. Ephemeroptera species composition, based on abundance and presence data, was evaluated in relation to niche and neutral predictors by using a partial redundancy analysis (pRDA). Results obtained through the pRDA indicated that both environmental and spatial processes influenced Ephemeroptera abundance. On the other hand, only environmental processes showed effects on community patterns when using species presence data from preserved, altered and large streams and also when looking only at the preserved sites. When streams larger than 20 m were excluded from analysis, both environmental and spatially processes showed influence on Ephemeroptera composition. Adjusted R 2 values were higher for environmental than for spatial processes in all analyses. The relatively high influence of both environmental processes and stream width in the analyses highlights the sensitivity of mayflies assemblies to environmental variation, and emphasizes the importance of local processes, as predicted by niche theory, while neutral processes act to a lesser extent on the structure of the studied communities.

We demonstrate that the distribution of the functional feeding groups of aquatic insects is related to hierarchical patch dynamics. Patches are sites with unique environmental and functional characteristics that are discontinuously distributed in time and space within a lotic system. This distribution predicts that the occurrence of species will be based predominantly on their environmental requirements. We sampled three streams within the same drainage basin in the Brazilian Cerrado savanna, focusing on waterfalls and associated habitats (upstream, downstream), representing different functional zones. We collected 2,636 specimens representing six functional feeding groups (FFGs): brushers, collector-gatherers, collector-filterers, shredders, predators, and scrapers. The frequency of occurrence of these groups varied significantly among environments. This variation appeared to be related to the distinct characteristics of the different habitat patches, which led us to infer that the hierarchical patch dynamics model can best explain the distribution of functional feeding groups in minor lotic environments, such as waterfalls.

ABSTRACT. Spatial distribution of trophic guilds and community structure of Ephemeroptera (Insecta) in streams of the Cerrado region in Mato Grosso, Brazil. We analyzed the structure of the functional feeding groups of Ephemeroptera in five different types of substrates (litter in riffles, backwater litter, wood, stones and roots) from first to fifth orders at the Pindaíba River basin, state of Mato Grosso, Brazil. We also studied the specificity and frequency of the organism, and if the functional approach reflects changes within the community through ordination analysis. Our results assemble information about the functional classification of mayfly nymphs and show that scrapers were the most abundant, and gathering -collectors are the more diverse. Third order streams were the most richest and most abundant while functional feeding group distribution corroborated the predictions of The River Continuum Concept. Besides, communities were much more taxonomically structured than functionally structured. This fact underlies the importance of the biology of organisms, and not only the functional feeding group, for substrate selection. The preference of some genera for specific substrates confirms this value. KEYWORDS.Taxonomic composition, aquatic insect, mesodistribution, indicator species.RESUMO. Analisamos a estrutura dos grupos funcionais alimentares de Ephemeroptera em cinco tipos de substratos (folhiço em corredeira, folhiço em remanso, madeira, pedras e raízes) de trechos de primeira a quinta ordens da bacia do rio Pindaíba, estado do Mato Grosso, Brasil. Verificamos, ainda, a preferência de táxons por substratos específicos através da especificidade e frequência dos organismos, e se a abordagem funcional reflete as variações dentro da comunidade. Nossos resultados agregam informações a respeito da classificação funcional dos efemerópteros e mostram que os raspadores foram os mais abundantes e os coletores-apanhadores comportam uma maior riqueza de táxons. Os córregos de terceira ordem foram os mais ricos e abundantes enquanto que as distribuições dos grupos funcionais alimentares corroboram as predições do Conceito do Continuum fluvial. Além disso, as comunidades estudadas foram muito mais estruturadas taxonomicamente do que funcionalmente. Esse fato atesta a importância da biologia dos organismos para a seleção dos substratos. A preferência de alguns gêneros por substrato específico corrobora esta importância. PALAVRAS-CHAVE. Composição taxonômica, insetos aquáticos, mesodistribuição, espécies indicadoras.O conceito de guilda alimentar foi proposto originalmente por Root (1967), definido como um grupo de espécies, indiferente da afiliação taxonômica, que exploram a mesma classe de recursos alimentares de uma maneira similar. Quando insetos aquáticos são divididos em guildas tróficas, essas categorias são conhecidas como grupos funcionais alimentares (Functional Feeding Groups -FFG), e são baseadas não só no tipo de recurso consumido, mas também nos mecanismos morfológicos e comportamentais de aquisição dess...