New palaeogeographic and lake‐level reconstructions of Lake Tanganyika: implications for tectonic, climatic and biological evolution in a rift lake

Abstract

Palaeogeographic and lake‐level reconstructions provide powerful tools for evaluating competing scenarios of biotic, climatic and geological evolution within a lake basin. Here we present new reconstructions for the northern Lake Tanganyika subbasins, based on reflection seismic, core and outcrop data. Reflection seismic radiocarbon method (RSRM) age estimates provide a chronological model for these reconstructions, against which yet to be obtained age dates based on core samples can be compared. A complex history of hydrological connections and changes in shoreline configuration in northern Lake Tanganyika has resulted from a combination of volcanic doming, border fault evolution and climatically induced lake‐level fluctuations. The stratigraphic expression of lake‐level highstands and lowstands in Lake Tanganyika is predictable and cyclic (referred to here as Capart Cycles), but in a pattern that differs profoundly from the classic Van Houten cycles of some Newark Supergroup rift basins. This difference results from the extraordinary topographic relief of the Western Rift lakes, coupled with the rapidity of large‐scale lake‐level fluctuations. Major unconformity surfaces associated with Lake Tanganyika lowstands may have corresponded with high‐latitude glacial maxima throughout much of the mid‐ to late Pleistocene. Rocky shorelines along the eastern side of the present‐day Ubwari Peninsula (Zaire) appear to have had a much more continuous existence as littoral rock habitats than similar areas along the north‐western coastline of the lake (adjacent to the Uvira Border Fault System), which in turn are older than the rocky shorelines of the north‐east coast of Burundi. This model of palaeogeographic history will be of great help to biologists trying to clarify the evolution of endemic invertebrates and fish in the northern basin of Lake Tanganyika.

Transposable elements and an epigenetic basis for punctuated equilibria

“…As predicted by the epi-transposon hypothesis, analysis of 75 SINE loci indicates that this haplochromine lineage has experienced repeated bouts of cichlid-specific SINE insertions followed by extensive radiations within each lake. (108) Moreover, geological evidence of aridification in East Africa 2.5-3 Mya (94) and extreme lake level fluctuations of several hundreds of meters over the last 1.1 My (109) is consistent with epigenetic regulation of cichlid TEs breaking down in response to environmentally induced physiological stress.…”

Ecological consequences of early Late Pleistocene megadroughts in tropical Africa

“…Prior attempts to date major diversification events within the cichlids (47,(51)(52)(53) have been based on the timing of the post-LGM lake-level rise and on much older, weakly constrained outcrop (54) or seismic data (55,56) from the two lakes. The megadrought low-stand demonstrated here for Lake Malawi provides a much more robust constraint on genetic divergence within the cichlid phylogeny, implying rates of evolution four to eight times slower than those that assume a major role for the LGM in Lake Malawi speciation.…”

A separate lowstand lake at the northern edge of Lake Tanganyika? Evidence from phylogeographic patterns in the cichlid genus Tropheus

“…These studies suggested mitochondrial introgression, sometimes on a small scale between presently allopatric populations, sometimes on a large-scale producing true hybrid populations, at various time points in the evolutionary history of the genus Tropheus. Most of these events of population displacement were triggered by lake level fluctuations, which extended to a few hundred meters below present level (Lezzar et al, 1996;Cohen et al, 1997;Scholz et al, 2003;McGlue et al, 2008). While the effect is widely seen in population genetic studies on various Lake Tanganyika cichlid species (Verheyen et al, 1996;Rüber et al, 1999Rüber et al, , 2001Duftner et al, 2006;Koblmüller et al, 2007Koblmüller et al, , 2009Koblmüller et al, , 2011Sefc et al, 2007;Nevado et al, 2013;Van Steenberge et al, 2015), studies specifically testing for the impact of Pleistocene water level fluctuations are scarce (Koblmüller et al, 2011;Winkelmann et al, 2016).…”