Holocene bidirectional river system along the Kenya Rift and its influence on East African faunal exchange and diversity gradients

René Dommain, Simon Riedl, Lydia A. Olaka, Peter deMenocal, Alan L. Deino, R. Bernhart Owen, Veronica Muiruri, Johannes Müller, Richard Potts, Manfred R. Strecker

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

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.

Original languageEnglish (US)
Article numbere2121388119
JournalProceedings of the National Academy of Sciences of the United States of America
Volume119
Issue number28
DOIs
StatePublished - Jul 12 2022

Bibliographical note

Funding Information:
ACKNOWLEDGMENTS. We are grateful to the Oldonyo Nyokie Group Ranch, the Olorgesailie project field team led by J. M. Muteti and J. N. Mativo, and the Siriata Maasai community, who allowed us to access their land. For their help during fieldwork, we greatly acknowledge Moses Saitoti, Oloishiro Kuresha, Nicholas Liarrash, George Gachie, and Ntai Kudate. We thank Angela Dial for laboratory support at Lamont, Tomasz Goslar (Poznan Radiocarbon Laboratory) for radiocarbon dating, and Herbert Tichy, Lukas R€uber, and Bettina Reichenbacher for their information on fish fossils. Pollen data were obtained from the Neotoma Paleoecology Database (https://www.neotomadb.org) and its constituent African Pollen Database. The work of data contributors, data stewards, and the Neotoma community is gratefully acknowledged. We are grateful for the constructive comments by two anonymous reviewers and the editors. R.D. was funded by a Smithsonian Human Origins Postdoctoral Fellowship and by Geo.X—the Research Network for Geosciences in Berlin and Potsdam. Fig. 1 D, E, and G and SI Appendix, Figs. S1 and S3 are based on the TanDEM-X Science DEM granted to L.A.O. and S.R. by the German Aerospace Center (DLR) in 2017. L.A.O. acknowledges the Volkswagen Foundation for funding this study with Grant No. 89369. M.R.S. and S.R. were supported by funds from Potsdam University and the Geothermal Development Company of Kenya, and R.B.O. and V.M. were supported by the Hong Kong General Research Fund. We acknowledge support from the National Museums of Kenya and the Kenya Government permission granted by the Ministry of Sports, Culture and the Arts, and by the National Commission for Science, Technology and Innovation (NACOSTI) Permits P/14/7709/683 (to R.P.) and P/16/11924/11448 (to L.A.O.). This work is a contribution of the Olorgesailie Drilling Project, for which support from the National Museums of Kenya, the Old-onyo Nyokie Group Ranch, the Peter Buck Fund for Human Origins Research (Smithsonian Institution), the William H. Donner Foundation, the Ruth and Vernon Taylor Foundation, Whitney and Betty MacMillan, and the Smithsonian Human Origins Program is gratefully acknowledged. LacCore is acknowledged for support in drilling and core storage.

Funding Information:
We are grateful to the Oldonyo Nyokie Group Ranch, the Olorgesailie project field team led by J. M. Muteti and J. N. Mativo, and the Siriata Maasai community, who allowed us to access their land. For their help during fieldwork, we greatly acknowledge Moses Saitoti, Oloishiro Kuresha, Nicholas Liarrash, George Gachie, and Ntai Kudate. We thank Angela Dial for laboratory support at Lamont, Tomasz Goslar (Poznan Radiocarbon Laboratory) for radiocarbon dating, and Herbert Tichy, Lukas R€uber, and Bettina Reichenbacher for their information on fish fossils. Pollen data were obtained from the Neotoma Paleoecology Database (https://www.neotomadb.org) and its constituent African Pollen Database. The work of data contributors, data stewards, and the Neotoma community is gratefully acknowledged. We are grateful for the constructive comments by two anonymous reviewers and the editors. R.D. was funded by a Smithsonian Human Origins Postdoctoral Fellowship and by Geo.X-the Research Network for Geosciences in Berlin and Potsdam. Fig. 1 D, E, and G and SI Appendix, Figs. S1 and S3 are based on the TanDEM-X Science DEM granted to L.A.O. and S.R. by the German Aerospace Center (DLR) in 2017. L.A.O. acknowledges the Volkswagen Foundation for funding this study with Grant No. 89369. M.R.S. and S.R. were supported by funds from Potsdam University and the Geothermal Development Company of Kenya, and R.B.O. and V.M. were supported by the Hong Kong General Research Fund. We acknowledge support from the National Museums of Kenya and the Kenya Government permission granted by the Ministry of Sports, Culture and the Arts, and by the National Commission for Science, Technology and Innovation (NACOSTI) Permits P/14/7709/683 (to R.P.) and P/16/11924/11448 (to L.A.O.). This work is a contribution of the Olorgesailie Drilling Project, for which support from the National Museums of Kenya, the Oldonyo Nyokie Group Ranch, the Peter Buck Fund for Human Origins Research (Smithsonian Institution), the William H. Donner Foundation, the Ruth and Vernon Taylor Foundation, Whitney and Betty MacMillan, and the Smithsonian Human Origins Program is gratefully acknowledged. LacCore is acknowledged for support in drilling and core storage.

Publisher Copyright:
Copyright © 2022 the Author(s). Published by PNAS. This open access article is distributed under Creative Commons Attribution License 4.0 (CC BY).

Keywords

  • biodiversity
  • biogeography
  • East Africa
  • Holocene
  • hydrological connectivity

Continental Scientific Drilling Facility tags

  • ODP

PubMed: MeSH publication types

  • Journal Article
  • Research Support, Non-U.S. Gov't

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