Rift Lake | ScienceGate

Located in the Ziway-Shala Basin of the Main Ethiopian Rift, Lake Langano is part of an asymmetric half-graben, defined by a series of north-northeast-trending faults in the tectonically active zone of the rift. A 15-m deep succession of organic homogeneous muds, silts, bioclastic sands, and pyroclastic layers was cored in 1994. The definition of a certified radiocarbon chronology on these deposits required the indispensable establishment of modern hydrological and geochemical balances. The isotopic contents of the total dissolved inorganic carbon (TDIC) of surface water clearly show the influence of a deep CO2 rising along the main fault crossing the lake basin. The 5.8 pMC disequilibrium existing in 1994 with the atmosphere likely produces the aging of authigenic materials developing at the lake surface. However, with a mean residence time of ~15 years, this apparent 14C aging of Lake Langano water still integrates the 14C produced by the nuclear tests in the 1960s. Reconstructing the natural 14C activity of the lake TDIC allows for the quantification of the deep CO2 influence, and for the correction of AMS-14C datings performed along the core. The correction of the AMS-14C chronology defined on Lake Langano allows for a better understanding of paleohydrological changes at a regional scale for at least the last 12,700 cal BP.

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Zeolites in Pleistocene sediments of an Ethiopian Rift lake

Zeitschrift der Deutschen Geologischen Gesellschaft ◽

10.1127/zdgg/150/1999/159 ◽

1999 ◽

Vol 150 (1) ◽

pp. 159-166

Author(s):

Wolfram Knoth ◽

Günter Knuth

Keyword(s):

Ethiopian Rift ◽

Rift Lake

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Adaptive Radiation

Ecology ◽

10.1093/obo/9780199830060-0214 ◽

2019 ◽

Author(s):

Linyi Zhang ◽

Scott P. Egan

Keyword(s):

Adaptive Radiation ◽

Evolutionary Process ◽

Ecological Traits ◽

Rapid Diversification ◽

African Rift ◽

Rift Lake ◽

Multiple Species ◽

Definition Of ◽

Life On Earth ◽

Diversity Of Life

The spectacular diversity of life on earth presents one of the most intriguing questions for biologists: why and how does the variation among organisms arise? One powerful concept that has its origins with Darwin (late 1800s) and was developed in detail during the Modern Synthesis (early to mid-1900s), is “adaptive radiation.” This evolutionary process refers to the rapid diversification of a single lineage into many different species during which different morphological/ecological traits evolve in association with different environments and niches. The central components of adaptive radiation are (1) rapid diversification of multiple species from a single common ancestor and (2) different species exhibit different ecological traits that are adaptive to different niches. While many great individual cases of adaptive radiation have been studied, such as Darwin’s finches, African rift lake cichlids, and Hawaiian silverswords, controversies remain on topics such as the definition of an adaptive radiation, the appropriate approach to test for it, and the ultimate causes of an adaptive radiation. This article provides a general overview of the literature addressing the study of adaptive radiation, including taxa-specific examples and major literature reviews. The article will highlight literature that helps to clarify the concept of adaptive radiation by distinguishing it from other related biological processes. Then the literature on specific approaches to test for adaptive radiation is featured. Next, connections to the literature aiming to understand the proximate and ultimate causes of adaptive radiation are provided, including explicit tests of the role of ecology, as well as an exploration of the source of genetic variation and geographic conditions promoting adaptive radiation. Lastly, we connect to the literature addressing the constraints on adaptive radiations. Overall, this article will address research on the origin of new species and the evolution of ecological differences between them.

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