Project Details
Projekt
A green corridor between Namib Desert and Kalahari? A phylogeographic view on the southwestern African climate during the Last Glacial Maximum
Subject Area
Physical Geography
Term
since 2024
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 551145135
The Last Glacial Maximum (LGM) is not only iconic for the understanding of the last glacial cycle but, as a well-defined period of extreme climate, represents a common compartment in climate models. Proxy-climate-reconstructions and climate models are not always in agreement and the global scale of many models is not sufficient to derive regional LGM climate conditions. The LGM climate of the so-called subcontinent Southern Africa has been discussed controversially. Beside geochronological uncertainties, the spatial distribution of geo-archives plays an important role. The position of the subcontinent between cold Atlantic and warm Indian Ocean on the one hand and the tropical rain belt in the north and the westerlies in the south on the other hand, triggered the creation of diverse ecosystems. There is no climate representative of the subcontinent and very likely that was also the case during the LGM. The dynamics of the climate sub-systems, however, can be compared between time slices. We here focus the southwest African drylands Kalahari and Namib which can be defined quite well, climatically and ecologically. Starting from our palaeontological evidence that certain river basins in the western Kalahari, which are dry nowadays, were permanently hydrologically active during the LGM, we aim at testing the hypothesis that the hydrographic network of the mountainous region between Kalahari and Namib was generally permanently active during the LGM. Consequently, a hydrographic connection (green corridor) between the (semi-) humid eco-regions north and south of the drylands did exist. The northwards shift of the westerlies could have triggered a favorable hydro-climate over the corridor during the LGM. The possibility to analyze geological outcrops exhibiting LGM fluvio-lacustrine sediments is limited and therefore we want to apply a methodological approach which is new for testing the green-corridor-hypothesis: The reconstruction of LGM migration pathways of the freshwater gastropod Burnupia spp. with genetic means (phylogeography). In case that the hydrographic network was active during the LGM, Burnupia spp. used it for migrations and genetic exchange occurred between populations which originally (and nowadays again) were restricted to regions north and south of the drylands. The period of genetic exchange can be dated using the molecular clock approach. Additionally, several hundred recent and LGM-dated shells of Burnupia populations will be morphometrically analyzed and compared, in order to identify the probable source areas (north versus south) of the fossil shells, and independent from the genetic approach. With the aid of remote sensing data, we will suggest where the connectivity between the different river systems (migrations bridges) was highest.
DFG Programme
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