Browsing by Author "Bryja, Josef"

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Evolutionary history and species diversity of African pouched mice (Rodentia: Nesomyidae: Saccostomus)
(Zoologica Scripta, 2016) Mikula, Ondrej; Sumbera, Radim; Aghova, Tatiana; Mbau, Judith S; Katakweba, Abdul S.; Sabuni, Christopher A; Bryja, Josef
We explore diversity of African pouched mice, genus Saccostomus (Rodentia, Nesomyidae), by sampling molecular and morphological variation across their continental-scale distribution in southern and eastern African savannahs and woodlands. Both mitochondrial (cytochrome b) and nuclear DNA (IRBP, RAG1) as well as skull morphology confirm the distinction between two recognized species, S. campestris and S. mearnsi, with disjunct distribution in the Zambezian and Somali–Maasai bioregions, respectively. Molecular dating suggests the divergence of these taxa occurred in the Early Pliocene, 3.9 Ma before present, whereas the deepest divergences within each of them are only as old as 2.0 Ma for S. mearnsi and 1.4 Ma for S. campestris. Based on cytochrome b phylogeny, we defined five clades (three within S. campestris, two in S. mearnsi) whose species status was considered in the light of nuclear DNA markers and morphology. We conclude that S. campestris group consists of two subspecies S. campestris campestris (Peters, 1846; comprising two cytochrome b clades) and S. campestris mashonae (de Winton, 1897) that are moderately differentiated, albeit distinct in IRBP and skull form. They likely hybridize to a limited extent along the Kafue–Zambezi Rivers. Saccostomus mearnsi group consists of two species, S. mearnsi (Heller, 1910) and S. umbriventer (Miller, 1910), that are markedly differentiated in both nuclear markers and skull form and may possibly co-occur in south-western Kenya and north-eastern Tanzania. Analysis of historical demography suggests both subspecies of S. campestris experienced population expansion dated to the Last Glacial. In the present range of S. campestris group, the distribution modelling suggests a moderate fragmentation of suitable habitats during the last glacial cycle, whereas in the range of S. mearnsi group it predicts substantial shifts of its occurrence in the same period.
Subspecific rodent taxa as the relevant host taxonomic level for mammarenavirus host specificity
(Elsevier Inc., 2023) Cuypers, Laura N.; Gryseels, Sophie; Baird, Stuart J.E.; Sabuni, Christopher A.; Katakweba, Abdul S.; van den Burg, Sebastiaan R.M.; Bryja, Josef; Leirs, Herwig; de Bellocq, Joëlle Goüy
Mastomys natalensis-borne mammarenaviruses appear specific to subspecific M. natalensis taxa rather than to the whole species. Yet mammarenaviruses carried by M. natalensis are known to spill over and jump hosts in northern sub-Saharan Africa. Phylogeographic studies increasingly show that, like M. natalensis, small mammals in sub- Saharan Africa are often genetically structured into several subspecific taxa. Other mammarenaviruses may thus also form virus-subspecific host taxon associations. To investigate this, and if mammarenaviruses carried by M. natalensis in southern Africa are less prone to spill-over, we screened 1225 non-M. natalensis samples from Tanzania where many small mammal taxa meet. We found mammarenavirus RNA in 6 samples. Genetic/genomic characterisation confirmed they were not spill-over from M. natalensis. We detected host jumps among rodent tribe members and an association between mammarenaviruses and subspecific taxa of Mus minutoides and Grammomys surdaster, indicating host genetic structure may be crucial to understand virus distribution and host specificity.