Abstract
ABSTRACT Based on the form-function interaction and its consequence to niche exploitation by fish species, the study aimed to identify ecomorphological patterns and to investigate the possibility of explaining the trophic niche breadth using the pattern of intraspecific ecomorphological diversity. We tested the following hypotheses: i) the morphology explains variations in diet among fish species; ii) the intraspecific ecomorphological diversity is related to the breadth of the trophic niche explored by the species, so that species that feed on a wider range of resources have greater variation in body shape compared to those specialized in resource consumption. Fish were collected in stands of the aquatic macrophytes Eichhornia azurea and Eichhornia crassipes in lentic environments of the Upper Paraná River floodplain, Brazil. Two major trends were observed in the morphological space: fish with body shapes adapted to explore the substrate and others with a design that facilitates the capture of food items in more structured habitats. The relationship of diet with body shape was confirmed by significant relationships between matrices of trophic and morphological distances, providing evidence that morphology is related to interspecific variations in the use of trophic resources. However, the ranges of morphological and intraspecific trophic variations were not significantly related, rejecting the second hypothesis about the relationship between intraspecific ecomorphological diversity and trophic niche breadth. The morphological characteristics often have multiple ecological roles, which could result in trade-off among these functions. Thus, fish with highly specialized morphology may show specialist feeding or even generalist habit, because in this case some resources may be difficult to exploit, even by a specialist. Species with low and high morphological diversity demonstrated narrow trophic niche and the availability of resources may have been essential for consumption. Therefore, species morphology is related to the use of food resources and ecomorphology can be considered an important tool for the prediction of the exploited niche space by species in assemblages. However it is not possible to predict if species with greater intraspecific morphological diversification indeed have wider niche, since the abundance or scarcity of the available food resources may interfere with trophic niche breadth.
Highlights
Ecomorphology is defined as the study of the relationship between body shape and use of resources among individuals, populations, guilds and communities (Peres-Neto, 1999)
Some authors attribute to the morphology the ability to predict the ecological niche - i.e., how the body shape selects the ecological space in a given habitat, and consider that ecomorphology can be used as a tool in analysis of assemblage structure (Winemiller, 1991; Casatti & Castro, 2006; Oliveira et al, 2010; Pagotto et al, 2011)
We collected 48 species, but only six were analyzed, since they achieved at least 5% of total caught specimens: Hyphessobrycon eques, Moenkhausia forestii, Serrapinnus calliurus and Serrapinnus notomelas, belonging to the order Characiformes; Apistogramma commbrae, Perciformes; and Pamphorichthys sp., Cyprinodontiformes
Summary
Ecomorphology is defined as the study of the relationship between body shape and use of resources among individuals, populations, guilds and communities (Peres-Neto, 1999). Morphological patterns in assemblages tend to characterize species groups that explore the same ecological resource - e.g., species in the same trophic guild may present a higher morphological similarity, independently of their phylogenetic distance (Oliveira et al, 2010), since the exploitation of specific food items in an ecosystem can be facilitated by a specific design (Wootton, 1992; Norton & Brainerd, 1993; Gerking, 1994; Norton, 1995; Winemiller, et al, 1995; Montaña & Winemiller, 2009; Sampaio et al, 2013) For this reason, some authors attribute to the morphology the ability to predict the ecological niche - i.e., how the body shape selects the ecological space in a given habitat, and consider that ecomorphology can be used as a tool in analysis of assemblage structure (Winemiller, 1991; Casatti & Castro, 2006; Oliveira et al, 2010; Pagotto et al, 2011). Correlation between morphological attributes and diet has been tested in ecomorphological hypotheses in fish assemblages (Pouilly et al, 2003)
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