Evidence of Niche Partitioning under Ontogenetic Influences among Three Morphologically Similar Siluriformes in Small Subtropical Streams

Abstract

Ontogenetic influences in patterns of niche breadth and feeding overlap were investigated in three species of Siluriformes (Heptapterus sp., Rhamdia quelen and Trichomycterus poikilos) aiming at understanding the species coexistence. Samplings were conducted bimonthly by electrofishing technique from June/2012 to June/2013 in ten streams of the northwestern state of Rio Grande do Sul, Brazil. The stomach contents of 1,948 individuals were analyzed by volumetric method, with 59 food items identified. In general Heptapterus sp. consumed a high proportion of Aegla sp., terrestrial plant remains and Megaloptera; R. quelen consumed fish, and Oligochaeta, followed by Aegla sp.; while the diet of T. poikilos was based on Simuliidae, Ephemeroptera and Trichoptera. Specie segregation was observed in the NMDS. Through PERMANOVA analysis feeding differences among species, and between a combination of species plus size classes were observed. IndVal showed which items were indicators of these differences. Niche breadth values were high for all species. The niche breadth values were low only for the larger size of R. quelen and Heptapterus sp. while T. poikilos values were more similar. Overall the species were a low feeding overlap values. The higher frequency of high feeding overlap was observed for interaction between Heptapterus sp. and T. poikilos. The null model confirmed the niche partitioning between the species. The higher frequency of high and intermediate feeding overlap values were reported to smaller size classes. The null model showed resource sharing between the species/size class. Therefore, overall species showed a resource partitioning because of the use of occasional items. However, these species share resources mainly in the early ontogenetic stages until the emphasized change of morphological characteristics leading to trophic niche expansion and the apparent segregation observed.

Trophic ecology of Hemigrammus marginatus Ellis, 1911 (Characiformes, Characidae) in a conserved tropical stream

“…Young individuals of the first standard length class consumed a large amount of zooplankton. The ontogenetic variations in freshwater fish diet have been commonly reported in the literature (Hahn et al, 2000;Lima-Junior and Goitein, 2003;Cassemiro et al 2008;Mazzoni and Costa, 2007;Agostinho et al, 2009;Suiberto et al, 2009;Abilhoa et al, 2010;Lima and Behr, 2010;Mazzoni et al, 2010;Bonato and Fialho, 2014). The ontogenetic variations found in the H. marginatus diet in the Beija-Flor stream are determined by the size of the fish, prey and ease of predation of available food resources, as the fish become adults, predation by the zooplankton item undergoes a significant decrease.…”

“…Ontogenetic variations in the diet during growth is a way to expand or change the niche of the species in order to avoid inter and intra-specific competition and maintain the shared resources (Bonato and Fialho, 2014). According to Cassemiro et al (2008), fish species with food plasticity have weak ontogenetic changes and a slight expansion in the niche breadth.…”

Ontogeny of feeding by Astyanax paris in streams of the Uruguay River Basin, Brazil

“…Mobility and higher competition capacity have often been cited as the aspects of larger fish prey selectivity (Russo et al, 2014). From this perspective, the ontogenetic shifts in the diet of A. paris can be viewed as a trophic strategy to reduce intraspecific competition, as seen in other Neotropical freshwater fish (Bonato and Fialho, 2014;Cavalheiro and Fialho, 2016;Dala-Corte et al, 2016).…”

“…The differential use of food resources is a wellknown intraspecific strategy to avoid trophic niche overlap between juveniles and adults in several freshwater fish species (Bonato and Fialho, 2014;Cavalheiro and Fialho, 2016;Dala-Corte et al, 2016). Some species may therefore concentrate on different food resources at different stages of their development (Rudolf and Lafferty, 2011).…”

Feeding ecology and resource sharing patterns betweenStellifer rastrifer(Jordan, 1889) andS. brasiliensis(Schultz, 1945) (Perciformes: Sciaenidae) along the coasts of Paraná and Santa Catarina, Brazil

“…MacArthur and Levins, 1967), species that are similar to others are predicted to have less opportunity to become abundant, owing to greater interspecific competition (Azzurro et al, 2014). Moreover, this could be a case of the 'ghost of competition past' (Connell, 1980), where resource partitioning is a consequence of negative interactions from past competition during the evolutionary process, eventually developing distinct and separate morphological and/or physiological characteristics (Pianka, 1974;Bonato and Fialho, 2014), allowing the exploitation of different resources and enabling coexistence in the same habitat.…”