Abstract
In this contribution we studied the trophic ecology of four Characidae species from the Cavalo Stream, upper Tocantins River, considering diet overlap and trophic niche breadth. The diet of the four species was composed of adult and immature insects, both autochthonous and allochthonous in origin. Autochthonous items dominated the diet of Moenkhausia dichroura (Kner, 1858), Bryconamericus sp., and Creagrutus atrisignum Myers, 1917. By contrast, allochthonous items were dominant in the diet of Astyanax bimaculatus (Linnaeus, 1758). Trophic niche breadth varied among species, with the highest value recorded for M. dichroura (0.48), followed by Bryconamericus sp. (0.39), A. bimaculatus (0.33) and C. atrisignum (0.29). Similarity analysis revealed two groups with different patterns of food preference. The first group was composed of insectivorous and the second by omnivorous species. The overlap in food items consumed by the four species studied was high. We suggest that resources are not limited in this stream and that competition might not be regulating these populations. This is one more case corroborating the general pattern registered for Tropical environments, where resource partitioning and specialization are responsible by the organization of fish communities.
Highlights
Fish communities are excellent models to test theoretical concepts about resource partitioning (ARANHA et al 1998, 2000, MOTTA & UIEDA 2004), niche breadth (CASATTI 2002) and niche overlap (DOUGLAS & MATTHEWS 1992, DOUGLAS et al 1994, NOVAKOWSKI et al 2008)
In this contribution we studied the trophic ecology of four Characidae species from the Cavalo Stream, upper Tocantins River, considering diet overlap and trophic niche breadth
Trophic niche breadth varied among species, with the highest value recorded for M. dichroura (0.48), followed by Bryconamericus sp. (0.39), A. bimaculatus (0.33) and C. atrisignum (0.29)
Summary
Fish communities are excellent models to test theoretical concepts about resource partitioning (ARANHA et al 1998, 2000, MOTTA & UIEDA 2004), niche breadth (CASATTI 2002) and niche overlap (DOUGLAS & MATTHEWS 1992, DOUGLAS et al 1994, NOVAKOWSKI et al 2008). Several studies carried out in tropical aquatic systems have demonstrated that one food resource can be consumed by many different fish species in a community. The first one, called “the niche theory”, considers that a niche is composed of different elements that supply the demands of a species and absorb the impacts of that species on the environment (CHASE & LEIBOLD 2003, NOBIS & WOHLGEMUTH 2004, MIKKELSON 2005). Resource partitioning and exploratory tactics to minimize feeding overlap, which represent alternatives to competition, are made possible by the great diversity of food items available, the great diversity of morphological adaptations, and the exploration of different microhabitats and periods of activity of species (HURLBERT 1978, CHASE & LEIBOLD 2003). We considered interspecific variations in diet composition, diet overlap, and trophic niche breadth
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