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.

Association Vahatra BP 3972 Antananarivo 101 Madagascar

Biology Department University of Antwerpen Evolutionary Ecology Group Groenenborgerlaan 171 2020 Antwerpen Belgium

College of Professional Studies Roosevelt University 430 S Michigan Avenue Chicago IL 60605 USA

Department of Botany and Zoology Faculty of Science Masaryk University Kotlářská 2 611 37 Brno Czech Republic

Field Museum of Natural History 1400 South Lake Shore Drive Chicago IL 60605 USA

Génoscope Centre National de Séquençage 2 rue Gaston Crémieux CP5706 91057 Evry Cedex France

Institut de Systématique Évolution Biodiversité ISYEB UMR 7205 CNRS MNHN UPMC EPHE Muséum National d'Histoire Naturelle Sorbonne Universités 57 rue Cuvier CP 51 75005 Paris France

Institute of Vertebrate Biology ASCR Academy of Sciences of the Czech Republic Květná 8 603 65 Brno Czech Republic

Royal Belgian Institute of Natural Sciences Operational Direction Taxonomy and Phylogeny Molecular Laboratory Vautierstraat 29 1000 Brussels Belgium

Université de Rennes 1 CNRS UMR 6553 Ecobio Station Biologique 35380 Paimpont France

Zoologisches Forschungmuseum Alexander Koenig Adenauerallee 160 D 53113 Bonn Germany

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