Long paleoecological records are critical for understanding evolutionary responses to environmental forcing and unparalleled tools for elucidating the mechanisms that lead to the development of regions of high biodiversity. We use a 1.2-My record from Lake Malawi, a textbook example of biological diversification, to document how climate and tectonics have driven ecosystem and evolutionary dynamics. Before ∼800 ka, Lake Malawi was much shallower than today, with higher frequency but much lower amplitude water-level and oxygenation changes. Since ∼800 ka, the lake has experienced much larger environmental fluctuations, best explained by a punctuated, tectonically driven rise in its outlet location and level. Following the reorganization of the basin, a change in the pacing of hydroclimate variability associated with the Mid-Pleistocene Transition resulted in hydrologic change dominated by precession rather than the high-latitude teleconnections recorded elsewhere. During this time, extended, deep lake phases have abruptly alternated with times of extreme aridity and ecosystem variability. Repeated crossings of hydroclimatic thresholds within the lake system were critical for establishing the rhythm of diversification, hybridization, and extinction that dominate the modern system. The chronology of these changes closely matches both the timing and pattern of phylogenetic history inferred independently for the lake's extraordinary array of cichlid fish species, suggesting a direct link between environmental and evolutionary dynamics.
|Original language||English (US)|
|Number of pages||6|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - Oct 18 2016|
Bibliographical noteFunding Information:
We thank all participants involved in the Lake Malawi Drilling Project, in particular Chris Scholz, Tom Johnson, Robert Lyons, and Eric Brown. We also thank Walter Salzburger for valuable discussion of cichlid evolution and Sylvia Dee for spectral analysis code. Initial core processing and sampling were conducted at LacCore at the University of Minnesota. Sample processing was conducted by Devin Gaugler, Chris Johnson, Jeanine Ash, and Claire DeCelles. Funding came from the US National Science Foundation-Earth System History Program (EAR-0602350); International Continental Scientific Drilling Program, American Chemical Society-PRF (54376-DNI8); and Smithsonian Institution. Partial sample preparation and analysis support was received from DOSECC, Chevron and BP summer scholarships, and UA SAGUARO.
© 2016, National Academy of Sciences. All rights reserved.
Copyright 2018 Elsevier B.V., All rights reserved.
- Adaptive radiation
- Cichlid evolution
- Tropical climate
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