Trophic resource partitioning is one of the main drivers of adaptive radiation. The evolutionary diversification of large African barbs, the genus Labeobarbus
, seems to be related to mouth polymorphism. The chisel-mouthed or scraping phenotype has repeatedly evolved within Labeobarbus
. At least five ecomorphs with a scraping mouth morphology were detected in the waters of the Ethiopian Highlands and can be provisionally classified into two groups: (i) “Varicorhinus
”-like, and (ii) “Smiling”-like. Previously, all Labeobarbus
with a scraping-mouth morphology were considered to be periphyton feeders. Using data on morphology, diet and stable isotope ratios (C and N), we addressed the question: does a scraping-mouth morphology predict feeding on periphyton? Our study revealed that five scraper ecomorphs exhibited three main feeding modes: (i) periphyton-eating, (ii) herbivory–detritivory, and (iii) insectivory. Two cases of the parallel divergence of sympatric ecomorphs with distinct feeding modes (herbivory–detritivory vs. insectivory) were revealed in two geographically isolated basins. A significant difference in δ15N values was detected among sympatric scraper ecomorphs. A periphytonophagous scraper was rich in δ15N values that are comparable with those in sympatric piscivorous fish. This data sheds light on the possibility of the utilization of periphyton as a protein-rich food by fishes.
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