Phylogeography and evolutionary history of the Crocidura olivieri complex (Mammalia, Soricomorpha): from a forest origin to broad ecological expansion across Africa.

François Jacquet,Violaine Nicolas,William T Stanley,Rainer Hutterer,Erik Verheyen,Marc Colyn,Steven M Goodman,Christiane Denys,Julian C Kerbis Peterhans,Josef Bryja,Arnaud Couloux

doi:10.1186/s12862-015-0344-y

Abstract

BackgroundThis 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.ResultsThe 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.ConclusionsClimatic 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-015-0344-y) contains supplementary material, which is available to authorized users.

Highlights

This study aims to reconstruct the evolutionary history of African shrews referred to the Crocidura olivieri complex
Phylogenetic relationships Based on Bayesian Inference of combined data from the seven markers (Figure 2 and Additional file 1) the C. olivieri complex forms a highly supported monophyletic group
Clades I, II, IV, VI and VIII are composed of specimens assigned to C. olivieri based on morphology

Summary

Introduction

This study aims to reconstruct the evolutionary history of African shrews referred to the Crocidura olivieri complex. There have been a few studies on sub-Saharan rodents [6,7,8], but shrews (Soricidae), a group known to have been used elsewhere to test Pleistocene climate oscillation models [9], have not been examined across broad ecological areas on the continent These animals have short life spans, rapid reproduction cycles, low dispersal abilities and respond quickly to environmental changes [10], and are a good model to investigate climate-driven models of diversification. Members of the C. olivieri complex occur in a variety of habitats, including tropical rain forests, marshes, savannah and montane areas [12] This group is a potentially excellent model to test how climatic oscillations and associated changes in vegetation during the Pleistocene influenced their distribution and diversification

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