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Title: Holocene bidirectional river system along the Kenya Rift and its influence on East African faunal exchange and diversity gradients
Authors: Dommain, René
Riedl, Simon
Olaka, Lydia A.
deMenocal, Peter
Deino, Alan L.
Owen, R. Bernhart
Muiruri, Veronica
Müller, Johannes
Potts, Richard
Strecker, Manfred R.
Keywords: Science::Geology
Issue Date: 2022
Source: Dommain, R., Riedl, S., Olaka, L. A., deMenocal, P., Deino, A. L., Owen, R. B., Muiruri, V., Müller, J., Potts, R. & Strecker, M. R. (2022). Holocene bidirectional river system along the Kenya Rift and its influence on East African faunal exchange and diversity gradients. Proceedings of the National Academy of Sciences of the United States of America, 119(28), e2121388119-.
Journal: Proceedings of the National Academy of Sciences of the United States of America 
Abstract: East Africa is a global biodiversity hotspot and exhibits distinct longitudinal diversity gradients from west to east in freshwater fishes and forest mammals. The assembly of this exceptional biodiversity and the drivers behind diversity gradients remain poorly understood, with diversification often studied at local scales and less attention paid to biotic exchange between Afrotropical regions. Here, we reconstruct a river system that existed for several millennia along the now semiarid Kenya Rift Valley during the humid early Holocene and show how this river system influenced postglacial dispersal of fishes and mammals due to its dual role as a dispersal corridor and barrier. Using geomorphological, geochronological, isotopic, and fossil analyses and a synthesis of radiocarbon dates, we find that the overflow of Kenyan rift lakes between 12 and 8 ka before present formed a bidirectional river system consisting of a "Northern River" connected to the Nile Basin and a "Southern River," a closed basin. The drainage divide between these rivers represented the only viable terrestrial dispersal corridor across the rift. The degree and duration of past hydrological connectivity between adjacent river basins determined spatial diversity gradients for East African fishes. Our reconstruction explains the isolated distribution of Nilotic fish species in modern Kenyan rift lakes, Guineo-Congolian mammal species in forests east of the Kenya Rift, and recent incipient vertebrate speciation and local endemism in this region. Climate-driven rearrangements of drainage networks unrelated to tectonic activity contributed significantly to the assembly of species diversity and modern faunas in the East African biodiversity hotspot.
ISSN: 0027-8424
DOI: 10.1073/pnas.2121388119
Schools: Asian School of the Environment 
Rights: © 2022 the Author(s). Published by PNAS. This open access article is distributed under Creative Commons Attribution License 4.0 (CC BY).
Fulltext Permission: open
Fulltext Availability: With Fulltext
Appears in Collections:ASE Journal Articles

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