Food-web structure in a subtropical coastal lake: how phylogenetic constraints may affect species linkages

摘要

To describe a food-web structure is a main goal in any attempt to understand ecosystem functioning. In the present study, we analysed the isotopic composition (δ~(13)C and δ~(15)N) of primary producers and consumers in the large subtropical Mangueira Lake in southern Brazil. On the basis of the 813C and 815N values and analysis of stomach contents of several fish species, we provide a description of the food-web structure and trophic positions of the dominant fish species. Analysis of nitrogen isotope ratios indicated the existence of two consumer trophic levels. Isotopic signatures of primary consumers were compatible with those of producers, indicating a food web sustained by autochthonous carbon. Nevertheless, when food items were classified in larger groups by relative size and source, the combined analysis of isotopic signature and feeding preferences revealed a phylogenetically structured arrangement for the fish species of Mangueira Lake. This indicates that the main feeding niches are shared by taxonomically related species.