Patterns of niche breadth and feeding overlap of the fish fauna in the seasonal Brazilian Pantanal, Cuiabá River basin

Abstract

Spatial and temporal variations in patterns of niche breadth and feeding overlap were investigated for the fish fauna in the Pantanal region, aiming to determine the factors that account for species coexistence. Samples were conducted in the Cuiabá River and Chacororé pond, in the upper Pantanal region, Mato Grosso State, Brazil, during one hydrological cycle (March 2000 to February 2001, (designed spatial-seasonal units). Mean niche breadth values were overall low for the fish assemblage (0.2-0.3). Differences between periods were not statistically significant. Feeding overlap values ranged between 0 and 0.4, whereas the mean was always inferior to 0.05 in all spatial-temporal units, and differences between periods were not statistically significant. The highest and lowest mean values were both observed in the pond; the former during the drought period and the latter during the flood period. All feeding overlap mean values were significantly higher than the values expected at random in the null model, using both "scrambled-zeros" (RA3) and "conserved-zeros" (RA4) algorithms. Thus, the foraging patterns show evidences of food sharing. The variance generated in the null model had a pattern similar to the niche overlap pattern: observed variance was higher than expected by chance in all spatial-temporal units, suggesting that the fish fauna is structured in trophic guilds. The patterns of food resource use and the different trophic guilds identified, suggest that species probably have different roles in this ecosystem. Our results suggest that food sharing allows coexistence of different fish species.Foram investigadas variações espaço-temporais nos padrões de amplitude de nicho e sobreposição alimentar da ictiofauna de uma região do Pantanal, com o objetivo de determinar os fatores responsáveis pela coexistência das espécies. Os peixes foram coletados no rio Cuiabá e na lagoa Chacororé, na região superior do Pantanal de Mato Grosso, Brasil, durante um ciclo hidrológico (março de 2000 a fevereiro de 2001) (designada unidade espaço-temporal). De modo geral, a ictiofauna apresentou baixos valores de amplitude de nicho trófico, sendo que as médias variaram entre 0,2 e 0,3 e não apresentaram diferenças significativas. Os valores de sobreposição alimentar foram igualmente baixos, entre 0 e 0,4 e as medianas em cada unidade espaço-temporal foram inferiores a 0,05, sendo que as diferenças não foram significativas. Os maiores e menores valores médios foram observados na lagoa, durante a seca e cheia, respectivamente, sendo essas diferenças significativas. Os valores médios de sobreposição alimentar foram significativamente maiores do que os esperados ao acaso no modelo nulo, usando tanto a opção de zeros embaralhados (RA3) quanto a de zeros retidos (RA4). Assim, os padrões de forrageamento das espécies mostraram evidência de compartilhamento de recursos alimentares. A variância acompanhou o mesmo padrão da sobreposição de nicho, sendo aquela observada sempre maior que a esperada ao acaso, indicando que a ictiofauna, de m...

Feeding ecology of Serrasalmus gouldingi (Characiformes: Serrasalmidae) in the lower Anapu River region, Eastern Amazon, Brazil

“…Some studies have evidence a more generalist diet during flood season (Luz- Agostinho et al 2008;Corrêa et al 2011), while others observed specialized diets during the same season (Sá-Oliveira et al 2014). Our results reinforce the hypothesis that there is no universal pattern in the exploitation of resources, but rather a variety of behavioral strategies related to the environmental characteristics of each system (Novakowski et al 2008).…”

Trophic relationships in fish assemblages of Neotropical floodplain lakes: selectivity and feeding overlap mediated by food availability

“…On the other hand, Matthews (1998) and Corrêa et al (2011) stated that when a resource is scarce, species could converge toward an almost identical use of the resource, and thus a high degree of overlap would occur. These conditions can have implications for competition for food resources (Pusey et al, 1995), which when it occurs tends to segregate species and reduces overlap.…”

Comparative feeding ecology of four syntopic Hypostomus species in a Brazilian southeastern river

“…In places where food overlapping uses to occur kinds of food and space may be recognized as the main axes as similar foods may occur in distinct microhabitats. Food and space are recognized as the main axes of resources to a niche division in vertebrates (Schoener, 1974), however Chase and Leibold (2003) state that related species living in a same community may present some type of differentiation (temporal or spatial) for the occupation of microhabitats. Some cases of spatial segregation of fishes presenting high overlapping indices for their feeding may occur as a consequence of historical differences between them in innate ability for habitat use and the absence of a species in a microhabitat (Edds et al, 2002).…”