Extreme trophic segregation between sympatric fish species: the case of small sized body Aphyocharax in the Brazilian Pantanal
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Interspecific differences in diet of the two sympatric fish species of the subfamily Aphyocharacinae were investigated. Both were sampled monthly (March 2000 to February 2001) during the rainy and dry season in North region of the Pantanal. Aphyocharax anisitsi was an invertivorous/insectivorous species, feeding mainly on aquatic insects during the rainy season and terrestrial insects in the dry season. Aphyocharax dentatus remained a piscivorous regardless of the hydrological season. Low feeding-overlap values, 0.079 in the dry season and no overlap in the rainy season were observed. The diet-breadth values for each species were low (less than 0.1) except for A. anisitsi in the lake during the dry season (0.4). A detrended correspondence analysis (DCA) summarized the diet similarity patterns: in DCA 1, it was observed that fish prey grouped A. dentatus in the lower scores, and insect prey grouped A. anisitsi in the higher scores. A two-way ANOVA showed that the diets differed significantly between the species. Our results show a clear trophic segregation between these species, supporting the niche concept that presumes that differences between sympatric species must exist, to allow their coexistence. Besides extreme segregation, it was clear that A. dentatus is a piscivorous fish, despite its low size (until 72 mm). This finding counteracts the current view about food web structure that poses a direct and positive relationship between body size and trophic position.
KeywordsAphyocharax anisitsi Aphyocharax dentatus Coexistence Diet Floodplain
We express our appreciation to Nupélia (Núcleo de Pesquisas em Limnologia, Ictiologia e Aqüicultura) and to PEA (Programa de Pós-graduação em Ecologia de Ambientes Aquáticos Continentais) for their financial and logistical support. To CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) for a postgraduate fellowship and to Sidinei Magela Thomaz for helpful suggestions. The language (English) was revised by Janet W. Reid (JWR Associates).
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