Unexpected Diversity of Feeding Modes among Chisel-Mouthed Ethiopian Labeobarbus (Cyprinidae)

Boris A Levin,Aleksandra S Komarova,Oksana L Rozanova,Alexander S Golubtsov

doi:10.3390/w13172345

Abstract

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.

Highlights

Ecological diversification is a cornerstone of the process of adaptive radiation, considered as one of the main sources of biodiversity emergence [1,2,3,4]
Our study revealed a diversification of ecological niches, based on the utilization of
“Varicorhinus”-like labeobarbs were described throughout Africa [16,29], a phenomenon of trophic resource partitioning were described throughout Africa [16,29], a phenomenon of trophic resource partitioning for this group was detected for the first time

Summary

Introduction

Ecological diversification is a cornerstone of the process of adaptive radiation, considered as one of the main sources of biodiversity emergence [1,2,3,4]. It is generally accepted that these cyprinids have a subterminal, often sectorial mouth, a cutting horny (keratinized) edge of the lower jaw, and a long gut scrape periphyton from submerged rocks and other substrates [18,20,21]. This type of scraping mouth structure, supplemented by an elongated gut, is found in many phylogenetically distant cyprinid lineages in North America

Methods

Results

Conclusion