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Large African barbs of the genus Labeobarbus constitute a hexaploid lineage (2n = 150). This group is widely distributed in African freshwaters, and exhibits profound phenotypic variation that could be a prerequisite for adaptive radiation.Using morphological, molecular, and stable isotope analyses, we investigated whether an adaptive radiation has occurred in a riverine assemblage of the Labeobarbus gananensis complex. This complex is composed of six phenotypically distinct sympatric forms inhabiting the Genale River (Ethiopian highlands, East Africa) in the Juba and Wabe–Shebelle drainages (Indian Ocean basin).Of the six forms, five were divergent in their mouth morphology, corresponding to generalised, lipped, scraping (two forms), and large‐mouthed phenotypes. One form had no mouth specialisation, but differed from the others in body shape (short and deep body; short form). Stable isotope analysis revealed differences in 15N among these forms, representing different foraging strategies (omnivorous, scraping, and piscivorous). Phylogenetic analysis of two mitochondrial DNA markers confirmed the monophyly of L. gananensis, suggesting an intra‐riverine radiation.However, the Genale assemblage appears to have originated through a combination of allopatric and sympatric events. Some of the specialised forms within the Juba and Wabe–Shebelle drainage originated independently from the local generalised forms in three different river regions. Each of these cases could be considered as a small species flock composed of two or three sympatric forms. Our study shows that adaptive radiation in rivers can be enhanced by a combination of sympatric speciation and temporal geographic isolation, leading to local sympatric speciation followed by migration. [ABSTRACT FROM AUTHOR]

Abstract: Based on morphological data and analysis of mitochondrial cytochrome b gene and nuclear (S7 intron 1) DNA sequences, the phylogenetic relationships of all Pollimyrus species known from the Omo‐Turkana enclosed basin and Nile system below the Murchison Falls were solved. A mormyrid “Pollimyrus” petherici is distantly related to all other studied Pollimyrus species and clusters together with Cyphomyrus species forming with the later a monophyletic group. Moreover, the West African (but not the Congo River) populations of Cyphomyrus psittacus, the type species of the genus, seem to be conspecific to C. petherici. That is, the range of the genus Cyphomyrus is extended toward the Nile and Omo‐Turkana basins. This genus belongs to the large clade widely distributed in sub‐Saharian Africa and characterized by the presence of a chin appendage. Significance of this character for mormyrid phylogeny is discussed. Two distinct lineages of Pollimyrus occurring sympatrically in the White Nile tributaries and previously reported as the light and dark forms of Pollimyrus isidori together with five other congeneric species studied form a monophyletic group. The light form apparently represents P. isidori distributed in the Nile system downstream of the Murchison Falls and West Africa; the dark‐colored form (designated as Pollimyrus “D”) represents a distinct phylogenetic lineage inhabiting both the Omo‐Turkana and the White Nile basin. Morphological and ecological data suggest that this form may be conspecific to East African Pollimyrus nigricans or most probably represents a new species. [ABSTRACT FROM AUTHOR]