Multilocus phylogeny of African striped grass mice (Lemniscomys): Stripe pattern only partly reflects evolutionary relationships

Murine rodents are one of the most evolutionary successful groups of extant mammals. They are also important for human as vectors and reservoirs of zoonoses and agricultural pests. Unfortunately, their fast and relatively recent diversification impedes our understanding of phylogenetic relationships and species limits of many murine taxa, including those with very conspicuous phenotype that has been frequently used for taxonomic purposes. One of such groups are the striped grass mice (genus Lemniscomys), distributed across sub-Saharan Africa in 11 currently recognized species. These are traditionally classified into three morphological groups according to different pelage colouration on the back: (a) L. barbarus group (three species) with several continuous pale longitudinal stripes; (b) L. striatus group (four species) with pale stripes diffused into short lines or dots; and (c) L. griselda group (four species) with a single mid-dorsal black stripe. Here we reconstructed the most comprehensive molecular phylogeny of the genus Lemniscomys to date, using the largest currently available multi-locus genetic dataset of all but two species. The results show four main lineages (=species complexes) with the distribution corresponding to the major biogeographical regions of Africa. Surprisingly, the four phylogenetic lineages are only in partial agreement with the morphological classification, suggesting that the single-stripe and/or multi-striped phenotypes evolved independently in multiple lineages. Divergence dating showed the split of Lemniscomys and Arvicanthis genera at the beginning of Pleistocene; most of subsequent speciation processes within Lemniscomys were affected by Pleistocene climate oscillations, with predominantly allopatric diversification in fragmented savanna biome. We propose taxonomic suggestions and directions for future research of this striking group of African rodents.

Chromosomal and molecular characterization of Aethomys kaiseri from Zambia and Aethomys chrysophilus from Tanzania (Rodentia, Muridae)

Aethomys is a common and widespread rodent genus in the African savannas and grasslands. However, its systematics and taxonomy are still unclear as no study has covered the entire range. In fact it might not be a monophyletic genus and perhaps should be split into two subgenera, Micaelamys and Aethomys. In this paper, we present findings based on the cytogenetics and the entire cytochrome b sequence of two species from Zambia (A. kaiseri) and Tanzania (A. chrysophilus), and we compare them with the sequences of a South African species (A. namaquensis) and other allied muroid genera. Comparison of the banded chromosomes revealed complete G-band homology between the autosomes of the two species. However, the X and Y chromosomes clearly differ in size and in C- and G-banding, being much larger in A. kaiseri. Comparison of the cytochrome b sequences places the separation between A. kaiseri and A. chrysophilus at 4.49 Mya, a period of intense speciation in other African muroids. The resulting phylogeny strongly supports the idea of a paraphyletic group, suggesting the need to elevate the previously described subgenera to the genus rank.