Respostas de um peixe de riacho à construção de uma rodovia na Amazônia: variação fenotípica inter e intrapopulacional e especialização individual,

Abstract

Human population growth and the endless demand for natural resources have resulted in dramatic changes in the environment, with severe impacts on the planet's biota. In this context, Brazilian streams have been heavily impacted, both indirectly by deforestation, land use, urban expansion, and directly by mining activities, construction of hydroelectric power plants and as a result of the construction of roads and highways. In the present Doctoral Dissertation, the phenotypic responses of the fish Bryconops giacopinii to the impacts of the damming of upland streams by the construction of a highway in the Amazon were analyzed, in relation to streams without apparent environmental impacts. Through field and laboratory studies, information was obtained about body shape, swimming performance, and their correlations with water temperature and current velocity in the habitats where the fish were collected. Body shape data were analyzed by geometric morphometry and swimming performance through a laboratory experiment, where the critical swimming speed (Ucrit) was estimated. The degree of individual trophic specialization was also verified through analysis of stomach contents and stable isotopes of Carbon (δ13C) and Nitrogen (δ15N) of tissues with different times of isotopic incorporation (liver, muscle and caudal fin). There was less phenotypic variation among individuals in the dammed streams, both within and between sites. It was also observed that fish from dammed streams showed changes in body shape compared to fish from intact streams, which presented a more hydrodynamic shape. Swimming performance was lower in fish from dammed streams, and this was correlated with the presence of parasites encysted on the fish’s skin (metacercariae). This set of results demonstrate that the homogenization of the habitat as a result of the damming of streams results in the selection of specific phenotypes, and these populations express less inter and intrapopulational variation, reflecting the simplification of the habitat caused by the impact of the damming of the streams by the highway. A higher degree of individual trophic specialization (both in diet and in isotopic composition) was detected in individuals from dammed streams, which is contrary to what was expected by the theory of niche variation. Such results emphasize the complexity of the phenotypic responses of organisms to environmental impacts and the context-dependent relationship of the degree of individual trophic specialization exhibited by individuals and population.