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

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.

Biogeographic origin and radiation of the Old World crocidurine shrews (Mammalia: Soricidae) inferred from mitochondrial and nuclear genes.

The crocidurine shrews include the most speciose genus of mammals, Crocidura. The origin and evolution of their radiation is, however, poorly understood because of very scant fossil records and a rather conservative external morphology between species. Here, we use an alignment of 3560 base pairs of mitochondrial and nuclear DNA to generate a phylogenetic hypothesis for the evolution of Old World shrews of the subfamily Crocidurinae. These molecular data confirm the monophyly of the speciose African and Eurasian Crocidura, which also includes the fossorial, monotypic genus Diplomesodon. The phylogenetic reconstructions give further credit to a paraphyletic position of Suncus shrews, which are placed into at least two independent clades (one in Africa and sister to Sylvisorex and one in Eurasia), at the base of the Crocidura radiation. Therefore, we recommend restricting the genus Suncus to the Palaearctic and Oriental taxa, and to consider all the African Suncus as Sylvisorex. Using molecular dating and biogeographic reconstruction analyses, we suggest a Palaearctic-Oriental origin for Crocidura dating back to the Upper Miocene (6.8 million years ago) and several subsequent colonisations of the Afrotropical region by independent lineages of Crocidura.

Molecular systematics and origin of sociality in mongooses (Herpestidae, Carnivora).

The Herpestidae are small terrestrial carnivores comprising 18 African and Asian genera, currently split into two subfamilies, the Herpestinae and the Galidiinae. The aim of this work was to resolve intra-familial relationships and to test the origin of sociality in the group. For this purpose we analysed sequences of the complete cytochrome b gene for 18 species of Herpestidae. The results showed that the mongooses were split into three clades: (1) the Malagasy taxa (Galidiinae and Cryptoprocta), (2) the true social mongooses and (3) the solitary mongooses, each group being also supported by morphological and chromosomal data. Our results suggested unexpected phylogenetic relationships: (1) the genus Cynictis is included in the solitary mongoose clade, (2) the genera Liberiictis and Mungos are sister-group, and (3) the genus Herpestes is polyphyletic. We examined the evolution of the sociality in mongooses by combining behavioural traits with the cytochrome b data. Some of the behavioural traits provided good synapomorphies for characterizing the social species clade, showing the potential benefit of using such characters in phylogeny. The mapping of ecological and behavioural features resulted in hypothesizing solitary behavior and life in forest as the conditions at the base of the mongoose clade.