Abstract
Morphological similarity, resource sharing, and differences in habitat use by species are factors that favor their coexistence. The objective of this study was to test possible differences in ecomorphology and diet composition of two Heptapterids (Imparfinis mirini and Cetopsorhamdia iherengi) to identify patterns related to resource use. Samplings were carried out in ten streams in Southern Brazil and 123 individuals were caught. A total of 21 ecomorphological indices were calculated for each individual and the volumetric and occurrence methods were used to quantify stomach contents. Both species presented significant differences in some ecomorphological traits, mainly related to foraging behavior. Even though both species were considered insectivorous, the consumed feeding resources differed between them. Cetopsorhamdia iheringi diet was dominated by Simuliidae and terrestrial Coleoptera larvae, while Imparfinis mirini, presented a diet dominated mainly by Trichoptera larvae, Ephemeroptera nymph, and Annelida. Although ecomorphological patterns cannot be used as an absolute factor to explain diet variations, they provide relevant information about how species share resources. These mechanisms allow us to obtain important subsidies for the conservation and management of freshwater ecosystems since they provide an effective understanding on the interactions that occur between the species.
Highlights
Trophic plasticity and the broad ecological niche allow the occupation of all trophic levels in aquatic environments by fish (Motta, Norton, & Luczkovich, 1995; Wootton, 1999; Abelha, Agostinho, & Goulart, 2001), which are the main organisms used in the ecomorphological studies (Moreira & Zuanon, 2002; Ramírez, Davenport, & Mojica, 2015)
Sampled fish were taken to the Núcleo de Pesquisa em Limnologia, Ictiologia e Aquicultura (Nupélia), of Universidade Estadual de Maringá (UEM), and specimens were deposited in the Ichthyological collection of Nupelia/UEM
When analyzing the first axis of Principal Component Analysis (PCA), it is observed that C. iheringi is located on the negative side presenting lower values for relative area of the pectoral fin (RAPeFi), relative area of the anal fin (RAAFi), relative area of the pelvic fin (RAPFi), reason-aspect of the pectoral fin, relative length of the head (RLH) and relative length of the caudal peduncle (RLCP)
Summary
Trophic plasticity and the broad ecological niche allow the occupation of all trophic levels in aquatic environments by fish (Motta, Norton, & Luczkovich, 1995; Wootton, 1999; Abelha, Agostinho, & Goulart, 2001), which are the main organisms used in the ecomorphological studies (Moreira & Zuanon, 2002; Ramírez, Davenport, & Mojica, 2015). The differentiation in the ecological niche as distinct use of habitats and resources allows their stable coexistence in the environment (Peres-Neto, 2004; Herder & Freyhof, 2006; Van Zwol, Neff, & Wilson, 2012). These may be related to adaptations in morphological traits, resulting in different ways of exploring the available resources (Labropoulou & Eleftheriou, 1997; Russo, Pulcini, O’Leary, Cataudella, & Mariani, 2008; Nandi & Saikia, 2015). Considering that morphology and diet are strongly correlated, the ecomorphology is an important tool to understand the exploited niche space and trophic segregation among coexisting species (Prado et al, 2016; Pease, Mendoza-Carranza, & Winemiller, 2018; Baldasso, Wolff, Neves, & Delariva, 2019)
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