Abstract
Though their broad distribution in most Brazilian rivers, scarce studies concerning ecological interactions on Hypostomus species are available. This study observes the diet, the trophic interactions and some morphological aspects of four syntopic species of Hypostomus. These fishes were studied at the superior part of the Corumbataí river, at São Paulo state, southeastern Brazil. Analyses focused feeding patterns, their amplitude and whether there happens some food items overlap among the species. Fish were caught using cast nets at some points of the river. Species were chosen according to their local abundance and, so there were four main species: H. albopunctatus, H. ancistroides, H. regani and H. strigaticeps. Nine food items were found: sediments, fungi, diatoms, green algae, Tecamoeba, vegetal debris and invertebrates. There were not significant differences for the feeding pattern among the four Hypostomus species. The feeding niche amplitude has been larger for H. albopunctatus influenced by a larger amount of vegetal debris and invertebrates. Elevated niche overlap was found to happen among the species and also for their trophic morphology. Results may suggest that there is a similar pattern in food taken between four species of Hypostomus analyzed since all consume similar environmental resources and have similar anatomical features. However, a different intake insect larvae and plant material in H. albopunctatus diet indicate differences in local and how this species may be exploring their food compared to the others.
Highlights
For ecological purposes it is important to evaluate which environmental conditions present limitations to communities (Cetra et al, 2011)
The analysis focuses in niche breadth, niche overlap between species and correlation of the diet with morphological features
The niche amplitude analyses for the four Hypostomus species showed the index to be larger for H. albopunctatus (Table 1) influenced by a higher consumption of plant material and invertebrate parts (Table 2)
Summary
For ecological purposes it is important to evaluate which environmental conditions present limitations to communities (Cetra et al, 2011). The resource utilization patterns constitute a fundamental mark of the ecological systems (Winemiller and Pianka, 1990), in which the food resources partitioning among coexistent species plays a more important role than that described even for the habitat partitioning inside aquatic environments (Schoener, 1974; Ross, 1986). Such a division may occur both in an intraspecific level as in an interspecific one (Gerking, 1994), and is seen as one the basic causes of population and community structurations (Tofoli et al, 2010). Mechanisms of living and interactions among species remain as a central theme for the populations ecology and niche differences have been evoked as fundamental to keep biodiversity in distinct scales (Leibold and McPeek, 2006)
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