Rapid chromosomal evolution in the mesic four-striped grass rat rhabdomys dilectus (rodentia, muridae) revealed by mtDNA phylogeographic analysis
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Date
2011-04-27
Journal Title
Journal ISSN
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Publisher
Blackwell Verlag GmbH
Abstract
The mesic four-striped grass rat Rhabdomys dilectus De Winton, 1897 is distributed in mesic regions of southern and eastern Africa. We carried
out a molecular and chromosomal study of the northernmost populations of the species to provide insight into the subspecific boundaries
identified within the species and to describe its genetic structure in Eastern Africa. Maximum likelihood, maximum parsimony and neighbour-
joining methods were used to construct phylogenetic relationships among all the haplotypes belonging to the large part of the species range. Times
of divergences were estimated assuming a relaxed molecular clock with two calibration points. We identified three well-supported clades within
R. dilectus. One basal clade corresponding to Rhabdomys d. chakae (2n = 48) is found in South Africa. Two additional sister clades
corresponding to R. d. dilectus (2n = 48 and 2n = 46) are allopatrically distributed in southern and northern parts of the species range. Genetic
divergence among the three clades is relatively high (ranges 4.2–5.7%). A very divergent new karyotype 2n = 38, FNa = 60 was found in two
high-altitude populations on Mt. Meru and Mt. Kilimanjaro. The karyotype differences consist in three Robertsonian fusions and one whole-arm
reciprocal translocation. Interestingly, the mtDNA phylogeny does not match with the diploid numbers. In fact, the 2n = 38 specimens form a
monophyletic group within a clade that includes specimens with the 2n = 46 karyotype that appears as paraphyletic. We estimated the new
karyotype originated in peripatric condition during the last phases of the Pleistocene. This study confirms the importance of chromosomal
analysis in detecting taxonomic units and cryptic diversity in rodents.
Description
Journal Zoological Systematic and Evolutionary Research
Keywords
African rodents, chromosomal evolution, cytochrome b, cytogenetics, cytotaxonomy, karyotype, phylogeography
Citation
doi: 10.1111/j.1439-0469.2011.00627.x