Abstract
BackgroundLake Tanganyika, an ancient lake in the Great Rift Valley, is famous for the adaptive radiation of cichlids. Five tribes of the Cichlidae family have acquired herbivory, with five ecomorphs: grazers, browsers, scrapers, biters and scoopers. Sixteen species of the herbivorous cichlids coexist on a rocky littoral slope in the lake. Seven of them individually defend feeding territories against intruding herbivores to establish algal farms. We collected epiphyton from these territories at various depths and also gathered fish specimens. Algal and cyanobacteria community structures were analysed using the amplicon-metagenomic method.ResultsBased on 454-pyrosequencing of SSU rRNA gene sequences, we identified 300 phototrophic taxa, including 197 cyanobacteria, 57 bacillariophytes, and 31 chlorophytes. Algal farms differed significantly in their composition among cichlid species, even in the same ecomorph, due in part to their habitat-depth segregation. The algal species composition of the stomach contents and algal farms of each species differed, suggesting that cichlids selectively harvest their farms. The stomach contents were highly diverse, even between species in the same tribe, in the same feeding ecomorph.ConclusionsIn this study, the amplicon-metagenomic approach revealed food niche separation based on habitat-depth segregation among coexisting herbivorous cichlids in the same ecomorphs in Lake Tanganyika.Electronic supplementary materialThe online version of this article (doi:10.1186/s12915-014-0090-4) contains supplementary material, which is available to authorized users.
Highlights
Lake Tanganyika, an ancient lake in the Great Rift Valley, is famous for the adaptive radiation of cichlids
Periphyton samples were simultaneously collected from five territories each of T. temporalis, V. moorii, P. macrognathus, P. polyodon, P. horii, P. trewavasae, T. moorii, dominant males of I. loocki and P. curvifrons, and breeding pairs of E. cyanostictus and X. papilio
Taxonomic assignment of the operational taxonomic units (OTUs) was performed by the Querycentric auto-k-nearest-neighbour (QCauto) method, using the software Claident v. 0.1.2012.05.21 [36,37]
Summary
Lake Tanganyika, an ancient lake in the Great Rift Valley, is famous for the adaptive radiation of cichlids. In Lake Tanganyika, five tribes of the family Cichlidae (Tropheini, Lamprologini, Ectodini, Eretmodini, and Tilapini) have acquired several ecomorphs that are closely related to feeding habits in herbivory such as grazing, browsing, scraping, biting, and scooping [10,11,12,13]. These tribes have no sexual dichromatism, and we can focus on the effect of ecological opportunity in the adaptive radiation of these herbivorous cichlids [14,15]. The fishes of each ecomorph have distinct specialised trophic morphologies in their jaw structures and intestine lengths [21,22], physiological abilities, such as secretion of digestive enzymes [21] and behaviours, such as cropping frequency [19]
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