Estrutura funcional das assembleias de peixes: padrões de diversidade processos ecológicos e conservação em ecossistemas aquáticos tropicais
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2014-03-25
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Universidade Federal de Goiás
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Species richness became a classical descriptor of biological communities, however, this concept does not encompass functional differences among species which may be linked to the functioning and the maintenance of ecosystem processes. For example, species with similar ecological traits should play similar ecological functions while species with distinct traits should play different functions. Understanding functional patterns of communities and how ecological processes act on their structuring is a challenge to ecologists, mainly in environments poorly known as tropical freshwater systems. In this context, the main goals of this thesis are to: i) test if the functional structure of headwater fish assemblages are influenced by drainage area and/or environmental components of basins; ii) comprehend the functional structure of river and headwater stream fish assemblages and evaluate the role of environment and spatial components on this structure; iii) test if functional diversity and species diversity patterns, besides spatial priorities for their conservation, are spatially congruent. The first objective was evaluated with a set of 25 headwater streams distributed in the Araguaia (13) and Tocantins (12) River basins. We tested for (dis)similarities among Araguaia and Tocantins fish assemblages with an analysis of similarities (ANOSIM), and we evaluated the role of space and environment on fish assemblages functional structure with RLQ and Fourthcorner analyses. We found a functional dissimilarity between fish assemblages of Araguaia and Tocantins (R = 0.09, p = 0.03) and RLQ was significant for trait/environment relationships (p = 0.005), although spatially structured environment also seems to be relevant. Altitude, channel depth, water temperature, turbidity and conductivity are environmental variables that influenced: body mass, water column position, substrate preference, parental care, foraging location and migratory habits. In this ways, fish assemblages' functional structure of Araguaia and Tocantins River basins are delimited is influenced by both space and local conditions of the environment. For evaluating the second objective, we calculate the net relatedness index (NRI) of 22 rivers and 27 headwater stream of Tocantins-Araguaia basin and related them with environmental variables of each watercourse. We used a variation partitioning for understanding how much of NRI variation could be explained by environment and/or space. The spatial pattern of NRI indicated that fish assemblages from headwater streams tend to be functionally clustered and from rivers overdispersed, and their separation is associated with four environmental variables: depth, width, water velocity and dissolved oxygen. However, variation partitioning indicated a lower influence of the environment on NRI variation when compared with the spatial components. Therefore, the functional structure of rivers and headwater streams is associated with neutral processes such as the dispersal limits of each species through the space. We evaluated the third objective using 21 units formed by the combination of one river and one headwater stream. Utilizing null models, we verified if units with higher species richness also have higher functional diversity. We created conservation scenarios for species richness and functional diversity with an algorithm of complementarity. No unit had higher functional diversity than expected by it species richness, which might indicate the possibility of developing a single conservation strategy for them. However, the congruence between conservation scenarios for species richness and functional diversity seems to be the result of the algorithm used that selects areas harboring species with restricted spatial occurrence, independently of other criteria used.
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CARVALHO, Rodrigo Assis de. Estrutura funcional das assembleias de peixes: padrões de diversidade processos ecológicos e conservação em ecossistemas aquáticos tropicais. 2014. 118 f. Tese (Doutorado em Ecologia e Evolução) - Universidade Federal de Goiás, Goiânia, 2014.