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Sympatric assemblage of cyprinid fishes of the genus Garra (Cyprinidae) from the Sore River, White Nile basin, East Africa: is it a species flock?

Boris A. Levin1*, Evgeniy Simonov1, Paolo Franchini2, Axel Meyer2 and Alexander S. Golubtsov3
  • 1 Institute of Biology of Inland Waters, Russian Academy of Sciences, Russia
  • 2 Universität Konstanz, Germany
  • 3 Severtsov Institute of Ecology and Evolution (RAS), Russia

The genus Garra is species-rich (more than a hundred species) lineage of cyprinids distributed from Southeast Asia to West Africa. Garra are mostly moderate-sized fish (usually less than 20 cm in length) with sucking mental disc that inhabiting the rhithron zone of river systems. The Ethiopian Highlands are the area of greatest Garra diversity in Africa (Stiassny & Abebe Getahun, 2007). Recently, an assemblage of several Garra morphs exhibiting extreme morphological diversity was discovered in the Sore River, the White Nile basin, in southwestern Ethiopia (Golubtsov et al., 2012). In particular, two morphs from the Sore display features not found elsewhere within the generic range: a form with a pronounced predatory morphology (large-sized, large-mouthed, with reduced sucking disk and a gut shorter than body length) and another with ‘rubber’ lips and prolonged snout region of head. Other morphs from the assemblage differ in mouth and sucking disc morphology and body shape. Our goals were to investigate the genetic background of this unusual Garra diversity in the Sore River and to test a hypothesis about sympatric origin of the assemblage. DNA samples (n=72) were collected from Garra inhabiting the Sore River near the City of Metu in 2012 and 2014. For comparison additional DNA samples (n=69) were collected from Garra species inhabiting the adjacent drainages. Sequences of the mitochondrial gene, cytochrome b (990 bp), was analyzed. A phylogenetic tree was reconstructed using both BI and ML approaches using available data from the Genbank for comparison. In addition, a ddRAD-seq analysis was performed for 42 individuals from the Sore River following the protocol of Franchini et al., (2017). The raw Illumina HiSeq reads were analyzed using STACKS (Catchen et al., 2013). STRUCTURE 2.3.4 (Pritchard et al., 2000) was used for analyses of population structure. Based on the preliminary morphological analysis, six morphs of Garra were distinguished in the Sore assemblage. According to mtDNA data, they clustered separately from the Garra inhabiting the adjacent drainages. This suggests monophyly of the Sore assemblage and would justify calling it “species flock” or an adaptive radiation. mtDNA markers could not resolve any relationships between these extremely closely related sympatric morphs. In spite of some mtDNA difference, the relationships between the mtDNA sequence and morphological variation could not be reconciled with certainty. The most plausible explanation for this phenomenon is incomplete lineage sorting. Our preliminary results of ddRAD-sequencing based on 42 individual samples (15850 SNPs at 35x coverage) for all six sympatric Garra morphs from the Sore River showed that we can distinguish four genetic clusters that correspond to four phenotypes. The two other phenotypes might be hybrids. Moreover, each of four genetic clusters showed some admixture from one or several of the other genetic clusters, possibly an indication of incipient speciation with incomplete reproductive isolation. The adaptive radiations in rivers draining the Ethiopian Highlands seem to occur in two phylogenetically distant lineages of cyprinids (the genera Garra and Labeobarbus – Levin et al., this volume-book). Based on mtDNA data, the Garra assemblage from the Sore River is monophyletic and can be treated as a “species flock” or an adaptive radiation. Additional effort is needed to clarify the population structure and phylogenetic relationships among sympatric Garra forms from the Sore River.

Acknowledgements

The study was supported by Russian Science Foundation (grant no. 19-14-00218). We are grateful to all members of Joint Ethiopian-Russian Biological Expedition, who participated in our field operations, and especially to Dr. A.A. Darkov, the expedition coordinator, for his permanent and invaluable aid.

References

Catchen, J., Hohenlohe, P. A., Bassham, S., Amores, A., & Cresko, W. A. (2013). Stacks: an analysis tool set for population genomics. Molecular ecology, 22(11), 3124–3140. Franchini, P., Monné Parera, D., Kautt, A. F., & Meyer, A. (2017). quaddRAD: a new high‐multiplexing and PCR duplicate removal ddRAD protocol produces novel evolutionary insights in a nonradiating cichlid lineage. Molecular ecology, 26(10), 2783–2795. Froese, R., & Pauly, D. (2018). FishBase 2018, version January, 2018. World Wide Web electronic publication Retrieved from http://www. fishbase.org. Golubtsov, A. S., Cherenkov, S. E., & Tefera, F. (2012). High morphological diversity of the genus Garra in the Sore River (the White Nile Basin, Ethiopia): one more cyprinid species flock? Journal of ichthyology, 52(11), 817–820. Pritchard, J. K., Stephens, M., & Donnelly, P. (2000). Inference of population structure using multilocus genotype data. Genetics, 155(2), 945–959. Stiassny, M.L.J. & Abebe Getahun. 2007. An overview of labeonin relationships and the phylogenetic placement of the Afro-Asian genus Garra Hamilton, 1822 (Teleostei: Cyprinidae), with the description of five new species of Garra from Ethiopia, and a key to all African species. Zoological Journal of the Linnean Society, 150, 41–83.

Keywords: African fishes, Mouth polymorphism, speciation, molecular genetics, adaptive radiation

Conference: XVI European Congress of Ichthyology, Lausanne, Switzerland, 2 Sep - 6 Sep, 2019.

Presentation Type: Poster

Topic: GENETICS, GENOMICS AND PHYSIOLOGY

Citation: Levin BA, Simonov E, Franchini P, Meyer A and Golubtsov AS (2019). Sympatric assemblage of cyprinid fishes of the genus Garra (Cyprinidae) from the Sore River, White Nile basin, East Africa: is it a species flock?. Front. Mar. Sci. Conference Abstract: XVI European Congress of Ichthyology. doi: 10.3389/conf.fmars.2019.07.00059

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Received: 17 May 2019; Published Online: 14 Aug 2019.

* Correspondence: Dr. Boris A Levin, Institute of Biology of Inland Waters, Russian Academy of Sciences, Borok, Russia, borislyovin@mail.ru