Background: This study aims to reconstruct the evolutionary history of African shrews referred to the Crocidura olivieri complex. We tested the respective role of forest retraction/expansion during the Pleistocene, rivers (allopatric models), ecological gradients (parapatric model) and anthropogenic factors in explaining the distribution and diversification within this species complex. We sequenced three mitochondrial and four nuclear markers from 565 specimens encompassing the known distribution of the complex, i.e. from Morocco to Egypt and south to Mozambique. We used Bayesian phylogenetic inference, genetic structure analyses and divergence time estimates to assess the phylogenetic relationships and evolutionary history of these animals. Results: The C. olivieri complex (currently composed of C. olivieri, C. fulvastra, C. viaria and C. goliath) can be segregated into eight principal geographical clades, most exhibiting parapatric distributions. A decrease in genetic diversity was observed between central and western African clades and a marked signal of population expansion was detected for a broadly distributed clade occurring across central and eastern Africa and portions of Egypt (clade IV). The main cladogenesis events occurred within the complex between 1.37 and 0.48 Ma. Crocidura olivieri sensu stricto appears polyphyletic and C. viaria and C. fulvastra were not found to be monophyletic. Conclusions: Climatic oscillations over the Pleistocene probably played a major role in shaping the genetic diversity within this species complex. Different factors can explain their diversification, including Pleistocene forest refuges, riverine barriers and differentiation along environmental gradients. The earliest postulated members of the complex originated in central/eastern Africa and the first radiations took place in rain forests of the Congo Basin. A dramatic shift in the ecological requirements in early members of the complex, in association with changing environments, took place sometime after 1.13 Ma. Some lineages then colonized a substantial portion of the African continent, including a variety of savannah and forest habitats. The low genetic divergence of certain populations, some in isolated localities, can be explained by their synanthropic habits. This study underlines the need to revise the taxonomy of the C. olivieri complex.
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The excavation campaign in 2011 focussed mainly on investigating the flatland settlement at the foot of the tell ‘‘Magura Gorgana’’. Three trenches respectively were explored in the area northeast and west of the settlement mound. Trenches H, L and P lie ca. 80 northeast of the centre of the tell, and trenches N1, N2 and N3 are located west of that midpoint. They yielded the hitherto oldest excavated material, which has already been radiocarbon dated. Excavations in the outer settlement of Pietrele have brought forth surprising and new perspectives. The oldest settlement attested until now can be dated to the end of the 6th millennium BC, and thus perhaps even to the Middle Neolithic. While a duration of 300 years (4250 to 4550 cal BC) has been confirmed for habitation of the tell, yet without reaching the native soil, find contexts from the end of the 6th and the first half of the 5th and end of the 5th millennium BC have come to light in the flatland settlement. Neolithic and Copper Age settlement remains are present in the immediate vicinity, which is not surprising for a site that was inhabited for a longer time. Hence, in Pietrele the possibility presents itself to research the horizontal stratigraphy of the flatland settlement, link it with the vertical stratigraphy of the tell settlement, and with that to control and render precise the chronological system for the Neolithic. At this point it can already be stated that the boundaries of the flat extended settlement were not reached by geophysical prospection in 2005, neither to the north nor to the west of the tell. Furthermore, geomorphological investigations have already gone far beyond the immediate area of the tell. More than 130 core drillings allow the conclusion that in the course of millennia flowing and standing bodies of water discharged into the Danube meadows. These meadows were covered by a large lake during the time of the tell’s habitation. Initial results of geochemical analyses confirm the existence of this expansive palaeolake before 4600 BC. The basic characteristics of the lake sediments include several massive phases of dark deposits, each a few decimetres in thickness, which are designated as ‘‘dark layers’’ (DL). They mark drastic events in the development of the lake. The lowermost layer, DL I, can be dated by the AMS-14C dating method to the 5th millennium BC, that is, the time of the tell’s habitation. Still to clarify is whether the introduction of organic material through settlement activities and land use had an adverse effect upon the quality of the water.
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