Influência do uso e ocupação do solo sobre as estruturas ecomorfológica e trófica de Imparfinis schubarti (Gomes, 1956) em um ribeirão periurbano e um rural

Abstract

The present study evaluated the effect of the pattern of land use and occupation of two sub-basins with different degrees of environmental disturbance on the ecomorphological and trophic structures of the fish species Imparfinis schubarti. The central hypothesis is that the different environmental characteristics of the studied basins tend to promote changes in the species' body shape and diet. For this, two sub-basins of the municipality of Londrina were delimited, one periurban (Cafezal river) and the other rural (Taquara river). The sampling areas were characterized according to land use and occupation, based on Landsat-8 images from the year 2013. The Maximum Likelihood, Minimum Distance, Parallelepiped and Spectral Angle mapping methods were tested. check which classifier has the best accuracy. Two hundred and seventeen individuals of the species I. schubarti were analyzed and for each 26 ecomorphological indices were calculated and their respective diets analyzed. Analysis of variance was applied to test for significant differences in the principal component analysis (PCA) scores of ecomorphological indices to verify whether individuals present different ecomorphological structures for each sub-basin. For food resources, the Relative Importance Index (IIR) was calculated and the extended correspondence analysis (DCA) was applied. Canonical correlation analysis (CCA) was applied to assess the correlations among abiotic data (land use and occupation) with biotic data (feeding). The thematic map of the Cafezal stream sub-basin was built using the Maximum Likelihood method and the Taquara river sub-basin with Spectral Angle Mapping. The Cafezal sub-basin had the highest percentages of urban area and the Taquara with the greatest coverage of agricultural area. Ecomorphological indices segregated individuals significantly, according to mobility and mouth opening. The DCA demonstrated that the individuals' diet segregated the rural sub-basin of Taquara, with greater diversity of food resources and preference for insects, vegetables, algae and fish eggs, while the periurban sub-basin of Cafezal verified the predominance of detritus. The CCA revealed that individuals from points 1 and 2 of Taquara tend to have a more specialized diet, associated with the presence of vegetation and agricultural use of the landscape, while individuals from point 3 of Cafezal tended to have a more generalist diet, which is related to greater use of the landscape by urbanization. The results revealed that individuals of the same species can present a significant intraspecific ecomorphological and trophic variation due to suffering different environmental pressures. Thus, these differences may indicate a probable process of local adaptation of the species to the new environmental conditions to which lotic systems are submitted.