Phylogeography of the Guinea multimammate mouse (Mastomys erythroleucus): a case study for Sahelian species in West Africa

Abstract

Aim To investigate the phylogeographical structure of the Guinea multimammate mouse, Mastomys erythroleucus (Temminck, 1853), a widespread murid rodent in sub‐Saharan (Sahel and Sudan) savannas, for a better understanding of the impacts of geographical and historical factors on the evolutionary history of this species, in the context of the growing database of phylogeographical studies of African savanna mammal species. Location Sahel and Sudan savannas, Africa. Methods We sequenced the whole cytochrome b gene in 211 individuals from 59 localities distributed from Senegal to Ethiopia. Sequence data were analysed using both phylogenetic (several rooted tree‐construction methods, median‐joining networks) and population genetic methods (spatial analyses of molecular variance, mismatch distributions). Results Haplotypes were distributed into four major monophyletic groups corresponding to distinct geographical regions across a west–east axis. Diversification events were estimated to have occurred between 1.16 and 0.18 Ma. Main conclusions Vicariance events related to the fragmentation of savanna habitats during the Pleistocene era may explain the phylogeographical patterns observed. Genetic structure was consistent with a role of major Sahelian rivers as significant barriers to west–east dispersal. Recent demographic expansions probably occurred during arid phases of the Holocene with the southward expansion of savannas.

Geographic patterns of inversion polymorphisms in a wild African rodent, Mastomys erythroleucus

“…Samples from Senegal and Mali were clustered into one group, those from Burkina-Faso and the westernmost one from Niger into a second one, the easternmost sample from Niger clustered with the one from Cameroon in a third group and finally the sample from Chad formed the fourth group. This longitudinal gradient of differentiation closely resembled the phylogeographical structure recently established using mitochondrial cytb sequences (Brouat et al, 2009). To further investigate this similarity, we sequenced the cytb gene of representatives from all (but three) newly sampled localities (GenBank accession numbers ranging between GQ409938 and GQ409966) and included in Brouat et al's (2009) data set, thus allowing the unambiguous attribution of each locality to one of the phylogeographic lineages (see Supplementary Figure and Supplementary Table).…”

“…For each specimen, at least five Gbanded metaphases were captured using a Zeiss microscope coupled to the Genus software (CytoVision), and used to prepare a minimum of two karyotypes. Brouat et al (2009) recently performed a phylogeographic analysis of M. erythroleucus based on complete cytochrome b (cytb) sequences. In total, 22 localities that they used are also included in this study (Supplementary Table).…”

“…In total, 22 localities that they used are also included in this study (Supplementary Table). In localities common to their and our own surveys but represented by different individuals, we considered all specimens trapped in the same locality (usually during the same field trip, often within the same trap lines) as belonging to the same cytb lineage sensu Brouat et al (2009). In the localities (n ¼ 27) not included in their molecular study, we sequenced at least one specimen per locality for the complete cytb mitochondrial gene (Supplementary Table).…”

“…In the localities (n ¼ 27) not included in their molecular study, we sequenced at least one specimen per locality for the complete cytb mitochondrial gene (Supplementary Table). To assign the latter specimens to a phylogeographic group, we then added these sequences to data set of Brouat et al (2009) and performed phylogenetic analyses following the same procedures (M. natalensis and M. huberti as out-groups; neighbor-joining with Tamura-Nei distances, maximum parsimony and maximum-likelihood analyses performed using PAUP version 4.0b (Sunderland, MA, USA); see Brouat et al, 2009, for details). Three localities (Gainsoa and Sotuba in Mali; Ile Madeleine in Senegal), not included in the previous phylogeographic survey, could not be molecularly investigated due to the unavailability of tissue samples.…”

“…We characterized pericentric inversion polymorphisms involving four chromosomal pairs in populations from West to Central Africa. The distribution pattern of chromosomal diversity was established and examined for signatures of several microevolutionary forces: (1) balancing selection by testing for heterozygote excesses and viability differences between cytotypes; (2) stochastic processes by comparing chromosome population structure to a molecular-based phylogeographic survey updated from Brouat et al (2009) and (3) long-term persistence by identifying the ancestral chromosomal forms in the genus.…”