Navegando por Orientadores "JUEN, Leandro"

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Acesso aberto (Open Access)
Determinantes da estrutura de comunidades de insetos aquáticos em riachos na Amazônia: o papel do habitat e da escala especial
(Universidade Federal do Pará, 2017-01-30) BATISTA, Gilberto Nicacio; HAMADA, Neusa; http://lattes.cnpq.br/1512994126787334; JUEN, Leandro; http://lattes.cnpq.br/1369357248133029
Aquatic ecosystems are highly complex environments, mainly due to interactions between their abiotic and biotic components; they are dependent on variation in physical structure and limnological characteristics, which in general, are factors that specifically act on different spatial and temporal scales. Therefore, considering this complexity in structuring stream habitats, particularly in Amazonian lotic ecosystems, this doctoral thesis aims to evaluate which are the determining factors to structure aquatic insect communities and their distribution according to environmental variation and geographical distances. To meet this goal the thesis is divided into four chapters. In the first, a systematic revision was carried out with a global assessment about the use of insects (Chironomidae: Diptera) in monitoring aquatic ecosystems and their responses as bioindicators. We found that the main issues presented in the studies were related to anthropogenic impacts on aquatic ecosystems and the taxonomic difficulties on the use of species identification to biomonitoring. The second shows analysis of distribution patterns and diversity of Chironomidae communities, under predictions of Metacommunity models, to evaluate the relations of the assemblages with the spatial scale and the environment. The main results showed that the assemblages were mainly affected by components of the physical habitat structure and partly the communities were limited by dispersal among the streams when considered at large scale in the region studied. The third showed analysis of functional composition on the communities of aquatic insects (Coleoptera, Diptera, Ephemeroptera, Hemiptera, Lepidoptera, Megaloptera, Odonata, Plecoptera, Trichoptera) and their responses to variation in habitat structure considered under the assumptions of the Habitat Templet. Overall, we found relationships between the distribution of morphological and functional traits with the physical habitat variables. The fourth chapter evaluates the effect of spatial distance on the community similarity of Ephemeroptera, Trichoptera, Plecoptera communities in two regions of Eastern Amazon. In this final chapter, we find differences in the composition of communities expressed as species replacement because of the geographical distance and local environmental characteristics of each region. Finally, the studies developed in this thesis summarized how the structure of the habitat of streams can affect the aquatic insect communities and variation in the riparian structure and physical habitat, can cause variation in taxonomical composition and functional attributes. In summary, from these findings, we conclude that the physical habitat variables are determining factors in structuring aquatic insect communities. In addition, it is highlighted the importance of local factors (riparian vegetation structure/composition of substrates/limnological characteristics) as explanatory variables for taxonomical and functional composition. In addition, the regional factors (geographical distance / dispersal limitation) are essential components to affect similarity and structure of the communities.
Acesso aberto (Open Access)
Ephemeroptera (Insecta) no Brasil: estado da arte, amostragem, influências e distribuição
(Universidade Federal do Pará, 2015) FEITOZA, Yulie Shimano; JUEN, Leandro; http://lattes.cnpq.br/1369357248133029
In this thesis we aimed to contribute to the ecological knowledge about the Ephemeroptera order in Brazil in order to decrease Wallacean, Prestonian and Hutchinsonian shortfalls related to these organisms. For this purpose, we worked with bibliographic data and field sampling, which resulted in six chapters. We summarized bibliographic information about Brazilian Ephemeroptera studies in the first chapter and for the others, we used data from collections performed in Brazilian Amazonia, also for the last chapter, we have used both dataset from collected and bibliographic source. In the first chapter, we performed a scienciometric analysis about Ephemeroptera studies in Brazil, then we have found the main gaps: absence of studies in some Brazilian states and records of families, need of studies about phylogeny, need of improvement of taxonomic resolution in ecological studies, and deficit of knowledge about environmental variables affecting Ephemeroptera distribution. In the second chapter, we proposed new sampler (circular handnet) and sampling design (150-meters along streams) to be used in ecological studies. We tested in the third chapter the effectiveness of our own methodology, where applied to verify whether 15 subsamples are enough to represent mayflies fauna (instead 20 subsamples), also discontinuos sampling are better than continuous, and if the taxonomic resolution between species and genera are highly concordants. In the fouth chapter, the community was analysed in a regional scale, where we verified differences in environment structure of streams and species composition according to interfluves and scales (local or regional). In the fifth chapter, we tested if River Hypothesis is valid for mayflies communities in Brazilian Amazon, where we found the largest rivers acting as geographic barriers structuring mayflies distribution, as well as the connection of drainage basins also affected Ephemeroptera distribution. Finally, in the last chapter we made a study of case through a new approach of Threshold Indicator Taxa Analysis (TITAN). In this chapter, we found Miroculis as a genus associated to forested areas while Ulmeritoides was associatedrelated to oil palm plantation areas;With this thesis, we increased records and knowledge of Amazonian mayflies, by reducing gaps in relation to distribution (Wallacean deficit), abundance (Prestonian defict) and environmental answers from these organisms (Hutchinsonian deficit).
Acesso aberto (Open Access)
Estruturação da comunidade de odonata (insecta) na Amazônia Oriental: efeitos espaciais, ambientais e morfológicos em igarapés íntegros e alterados
(Universidade Federal do Pará, 2015-12-04) OLIVEIRA JUNIOR, José Max Barbosa de; JUEN, Leandro; http://lattes.cnpq.br/1369357248133029
Acesso aberto (Open Access)
Filtros ambientais determinando caracteres funcionais de assembleias de Odonata
(Universidade Federal do Pará, 2017-03-24) PEREIRA, Diego Fernandes Gomes; JUEN, Leandro; http://lattes.cnpq.br/1369357248133029
Species distribution is affected by availability of habitas that fit within the limits of variation of their niche and by interaction with other species. Environmental modifications, especially those of anthropic origin, are increasingly common, and are considered major causes of species extinction during the Anthropocene. Aquatic ecosystems are considered among the most vulnerable on the planet because of its dependence on the surroundings and the drainage system. However, species responses to these changes are not random, and can follow patterns that are caused by the specific functionality or morphology of each taxon. This work’s goal was to evaluate if environmental factors work as ecological filters for the establishment of Odonata species through selection of their functional and morphological characters, testing the hypotheses that a) the environment works as a filter over species, by facilitating or hindering characters and b) that due to their thermoregulatory and reproductive requirements, indispensable for colonization and population maintenance, thorax width and oviposition type will be the most affected biological variables. Considering that, we sampled 97 streams in the oriental side of the Brazilian Amazon Forest, distributed over an environmental gradient which covers areas ranging from untouched primary forest to areas extremely modified by agriculture and livestock. We used six functional traits (total body length, fore wing length, fore wing width, thorax width, abdominal length and oviposition type) and seven environmental variables (habitat integrity index, dissolved oxygen, water temperature, canopy cover, macrophytes cover, pH and condutivity). To evaluate if the environmental variables affected the odonate communities, we used the combination of the RLQ and Fourth Corner analysis, with which we assessed the relation between each of the selected traits with each of the habitat descriptors. Among the studied environmental variables, habitat integrity index presented the largest effect over the community of Odonata, having a negative relation with fore wing width, thorax width and exophytic oviposition, and a positive relation with endophytic oviposition. Macrophytes cover showed a negative relation with abdominal length and a positive relation with thorax width and exophytic oviposition. No other environmental descriptor presented significant relations. The results show that poorly preserved habitats facilitate the occurrence of organisms with larger thorax and the substitution of the endophytic by the exophytic type of oviposition. Since environmental impacts usually do not change Odonata species richness, only community composition, these results point that there is favouritism towards groups of species with those characters, like the Libellulidae family, with detriment to other families or groups (specially of the Zygoptera suborder), what might result in community homogeneity and loss of functional and phylogenetic diversity. Thus, the preservation of primary forest is indispensable for the maintenance of Odonata, being the best way to conserve the different ecophysiological and behavioural groups in the order. The dragonfly communities’ responses, directed by morphological and behavioural traits, enlightens ecological response patterns, and the addition of oviposition categories to conservation policies for the Odonata is critical in making them more effective, as they are absolutely necessary for population stability and colonizing new sites.
Acesso aberto (Open Access)
Padrões de distribuição de espécies de percevejos semi-aquáticos (Hemiptera: Gerromorpha): utilizando fatores ambientais e espaciais para determinar a estrutura das comunidades em riachos amazônicos
(Universidade Federal do Pará, 2018-08-02) CUNHA, Erlane José Rodrigues da; JUEN, Leandro; http://lattes.cnpq.br/1369357248133029
Amazonian lotic ecosystems are among the environments that have received most attention in studies on species distribution. This is related to the presence of high environmental complexity and spatial variation in these ecosystems, thus it is necessary to elucidate how such conditions affect the species distribution in response to habitat specificity and dispersion under different scales. Thus, in this thesis we aim to evaluate how environmental and spatial factors structure semi-aquatic bug (Hemiptera: Gerromorpha) communities in Amazonian streams. To achieve this goal, the thesis was divided into three chapters. First, we evaluated factors that structure metacommunities, considering environmental factors, linear and fluvial spatial structure within a drainage basin. We observed that the effect of the environment had greater effect on metacommunity structure and only factors related to river dispersion were important for these response. Thus, at basin scale, the metacommunity structure was affected mainly by species sorting and mass effects was associated to dispersion in smaller scales within basin network. In second chapter, we analyzed the patterns of metacommunities of semiaquatic bugs among different biogeographic areas of the Amazon region, we found that the limitation of community variation across space was decisive in structuring the diversity of assemblies. These results showed that high turnover occurs within the ecoregions evaluated due to environmental heterogeneity. In addition, beta diversity between different biogeographic areas in Amazon region evidenced general patterns of decay of similarity due to environmental and spatial distances. In the third chapter, we deconstructed the assemblages between wingless and winged individuals to evaluate the alteration of the environment in areas with anthropic alteration. We find that the composition of winged species assemblages differs from the total community composition, however, assemblages of winged and winged species showed responses associated with the loss of diversity caused by anthropic activity. However, the environmental variables that structure these assemblies were different, indicating that a trade-off occurs between reproduction (wingless) and dispersion (winged) to reach the fitness of these populations. In general, we highlight that characteristics of the aquatic habitat on a local scale, and the fluvial connectivity between habitats are the main determinants in structuring the communities of these organisms at a basin scale. Considering biogeographic scales, the limitation of the dispersion through space was the main factor in the structure of the communities, however, the beta diversity between regions also showed to be dependent on local factors. We consider that the specificity of these organisms to live on the surface of the water, besides showing strong relation with this habitat, also shows that the locomotion on the water surface is the main dispersion mechanism of these organisms in the basin network. In addition, the processes that have determined communities' patterns of diversity act on local scales up to biogeographic scales. However, we highlight that advances in the impacts of anthropic activities in the Amazon can also interfere in these processes and act on the distribution of species among the lotic ecosystems of the region.
Acesso aberto (Open Access)
Padrões de diversidade e suas implicações para a conservação de Odonata (Insecta) em igarapés amazônicos
(Universidade Federal do Pará, 2018-08-03) BRASIL, Leandro Schllemmer; JUEN, Leandro; http://lattes.cnpq.br/1369357248133029
The distribution of species within a landscape and the mechanisms that determine this distribution are fundamental questions for the understanding of the ecology of biological communities. The understanding of these phenomena is essential for the management of ecosystems and decision-making on the conservation of biodiversity, environmental conditions, and ecosystem resources. In this dissertation, we focused on the communities of the damselflies, suborder Zygoptera (Insecta: Odonata), found in streams in the Brazilian Amazon region to investigate their alpha diversity (Chapter 1), beta diversity (Chapter 2), and the elements that structure metacommunities (Chapters 3), as well as the spatial priorities for the conservation of Amazonian odonates (Chapter 4). We used environmental, biogeographic, and spatial predictors to investigate the mechanisms that structure the distribution of the communities analyzed in this dissertation. In the case of alpha diversity (Chapter 1), environmental heterogeneity (climate) and primary productivity were the most important determinants of zygopteran species richness. For beta diversity (Chapter 2), turnover was the most important component of changes in species composition within the landscape, together with the spatial distance between sites, and the biogeographic region (centers of endemism), which were the most important predictors of zygopteran beta diversity. In our analysis of metacommunity patterns (Chapter 3), we found a Clementsian pattern in well-preserved streams, with a major change in the configuration of the communities in streams with environmental alterations, which represented subsets of the better preserved areas. In Chapter 4, we show that the spatial distribution of the conservation units in the Amazon region is relatively ineffective for the conservation of most of the beta diversity of the region’s odonates. As the priority areas are located predominantly in southern Amazonia, and most of these areas have already been deforested, given that they lie within the arc of deforestation, the priority areas were displaced toward the forested environments located nearer the center of the Amazon region. Based on this analysis, we suggest the creation of new conservation units or the implementation of incentives for the establishment of activities that cause reduced environmental impacts in more central, priority areas, which are still forested, as well as 4 the restoration of priority areas that have already been deforested. One possibility here would be the implementation of programs that pay for ecosystem services, such as carbon credits obtained through reforestation and/or the development of activities with a reduced impact on biodiversity, such as agroforestry. This study also makes a major contribution to the reduction of the Wallacean and Hutchisonian shortfalls on the zygopterans of the Brazilian Amazon region.