Fishes in the desert: mitochondrial variation and phylogeography of Danakilia (Actinopterygii: Cichlidae) and Aphanius (Actinopterygii: Cyprinodontidae) in the Danakil Depression of northeastern Africa

Abstract

The Danakil Depression in northeastern Africa represents one of the harshest arid environments on Earth, yet two genera of fishes, Danakilia (Cichlidae) and Aphanius (Cyprinodontidae), share its sparse aquatic habitats. The evolutionary history of these fishes is investigated here in the context of genetic, geological and paleoenvironmental information. We collected samples from seven sites and assessed phylogeographic relationships using concatenated COI and cytb mtDNA genes. Danakilia morphospecies show low differentiation at mitochondrial markers, but variation is partitioned between a northern cluster containing D. dinicolai plus three undescribed riverine populations, and a southern cluster including two creek populations of D. franchettii separated by the hypersaline waters of Lake Afrera. Aphanius displayed four genetically distinct clades (A. stiassnyae in Lake Afrera; one distributed across the entire area; one in Lake Abaeded; and one in the Shukoray River), but without clear large-scale geographic structure. However, Danakil Aphanius are clearly differentiated from A. dispar sensu stricto from the Sinai Peninsula. Geological evidence suggests that after the Late Pleistocene closure of the Danakil-Red Sea connection, increased post-glacial groundwater availability caused the formation of a brackish paleo-lake flooding the entire region below the –50 m contour. Fish populations previously isolated in coastal oases during glaciation were able to mix in the paleo-lake. Subsequently, in a more arid phase starting ∼7300 BP, paleo-lake regression isolated fishes in separate drainages, triggering their still ongoing diversification.

Keywords:

• Africa; Aphanius dispar
• Aphanius stiassnyae
• clade diversification
• Danakilia
• extremophile fishes

Acknowledgements

We wish to thank the Eritrean authorities for access permits to restricted areas of the Northern Red Sea Region and the Eritrean Ministry of Marine Resources for granting research and export permits. Our gratitude also to the Ethiopian Biodiversity Institute for issuing research and export permits. In particular, we wish to thank Abraham Assefa, director of Animal Biodiversity Directorate, and the Afar Regional State authority for allowing transit and stay in Afar, and for providing a guide and local police protection. We are grateful to Futsum Hagos who, in a friendly fashion, provided his professional experience about the Danakil desert and its people during two research trips, and to his supervisor Abraha Garza (Forestry and Wildlife Authority of Eritrea) who heartily supported Futsum’s participation to the expeditions. Anton Lamboj participated to the first expedition in Eritrea and provided valuable help and suggestions during the collection of samples. Eleonora Boncompagni, Haile Hailemical and Tesfu Fekensa gave their unconditioned assistance during two successive field trips in Eritrea and Ethiopia. Ernesto Abbate, Jörg Freyhof, Abebe Getahun, Massimiliano Ghinassi and Stefano Valdesalici gave valuable scientific input on various occasions. Anton Weissenbacher (Vienna Zoo) and Marco Benedet provided Aphanius samples from captive bred Shukoray and wild Sinai Peninsula populations, respectively. Gianpasquale Chiatante developed the Digital Elevation Model and GIS renderings that gave substance to our theoretical intuitions. Gianni Ghezzi (Le Onde Cichlids) generously provided technical supplies for field collection and successive captive breeding of Danakilia specimens. Our thanks to the Associazione Italiana Ciclidofili for support for the Lake Afrera field expedition. Finally, we are particularly grateful to Giampaolo Montesanto (Asmara) and Paola Marras with her family (Addis Ababa) for hospitality, and to the elders and people of the villages of Adaito and Badda (Eritrea) for their whole-hearted assistance in their villages and in the field, and to Danakali Limited for use of facilities at their base camp in the Colluli area (Eritrea).

Disclosure statement

The authors report no conflicts of interest and are alone responsible for the content and writing of the paper.