Ecologia de comunidades de turbelários límnicos em áreas úmidas do sul do Brasil
Braccini, João Alberto Leão
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DescriptionOne of the big challenges in ecology is trying to understand the patterns of community structure and their variations along environmental gradients. Among these gradients, habitat complexity is related to several environmental characteristics, such as: topographic complexity or substrate roughness, substrate diversity, refuge variety, substrate height, percentage of vegetation cover and vegetation composition, which have a strong influence on communities. Intermittent wetlands have an annual hydroperiod, being characterized by unique fauna and flora that contribute significantly to the local diversity. In turn, permanent wetlands have water throughout the whole year and water staying for long periods allows the occurrence of non-ephemeral species. Altitude is a condition that strongly influences the climate of a region and consequently its biota, an increase in altitude causes diminution in mean temperature, changes in terrain, topography and hydrography, which lead to changes in the general structure of communities. A spatial approach, on the other hand, implies that geographical distance can influence community structure, i.e., the greater the distance between two communities, the less similar they should be. The main objective of this thesis is to analyze the influence of local and regional factors on the richness, abundance and species composition of turbellarian species in freshwater environments in southern Brazil along a series of environmental gradients. The samples occurred in 40 natural wetlands in highland environments (Araucaria Plateau) and along the whole coast of the state of Rio Grande do Sul, between the years 2016 and 2017. A total of 3008 turbellarian specimens of 76 species was collected. In highland environments, the factors hydroperiod, habitat complexity, total dissolved solids (TDS) and, for richness, also pH, considering seasonal variations, were the factors that best-explained variations in turbellarian richness and abundance. There was also influence of these variables on species composition (p < 0.05). Turbellarian species richness was higher in coastal wetlands than in highland wetlands (p < 0.05). The turbellarian communities were distinct between highland and coastal wetlands (p <0.05) with exclusive taxa for both wetland groups, where TDS was an important variable for species composition. Across a latitudinal gradient in Coastal Plain, species richness presented correlation to space, with the highest stimated values in middle coast, and species richness showed a positive relation to phytoplankton density and negative to salinity (p < 0.05). We observed the highest estimated specimen abundance in the south coast; there was a positive relationship between specimen abundance and an increase of turbidity and a decrease of dissolved oxygen (p < 0.05). Species composition was weakly explained, with a significant relation to salinity and turbidity (p < 0.05). The results of this study highlight how dynamic and complex turbellarian communities are, with the direct influence of local and regional factors on richness, abundance and species composition. There was an expressive increase in the knowledge of factors that influence these invertebrate communities in natural neotropical wetlands.
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