Application of a multidisciplinary approach to the systematics of Acomys (Rodentia: Muridae) from Northern Tanzania
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Date
2006-12
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Abstract
The systematic status and geographic distribution of spiny mice of the genus Acomys I.
Geoffroy, 1838 in Northern Tanzania is uncertain. This study assesses the systematic and
geographic distribution of Acomys from Northern Tanzania using a multidisciplinary
approach that includes molecular, cytogenetic, traditional and geometric morphometric
analyses, and classical morphology of the same individuals. The molecular analysis was
based on 1140 base pairs (bp) of the mitochondrial cytochrome b and 1297 bp of the
nuclear interphotoreceptor retinoid binding protein (IRBP) gene sequences. These data
were subjected to phylogenetic analyses using Maximum likelihood, Bayesian, Maximum
parsimony, and Minimum evolution analyses. The cytogenetic analysis included G-banding
of metaphase chromosomes. The morphometric analyses included univariate and
multivariate analyses of traditional morphometric measurements of the cranium and
mandible, and of geometric morphometric two-dimensional landmarks of the dorsal,
ventral, and lateral views of the cranium, and lateral view of mandible that included thinplate
spline (TPS) analysis. The classical morphology included examination of external,
cranial and mandibular morphology. Results of all these multidisciplinary analyses were
congruent and provide evidence for the occurrence of two sympatric species of Acomys in
northern Tanzania, namely, the previously recorded A. wilsoni (2n = 62) and a newly
recorded A. cf. percivali (2n = 58). These results that also represent the first reported
mitochondrial cytochrome b and nuclear IRBP gene sequences and karyotype for A. cf.
percivali, increases the number of species known to occur in Tanzania from four to five.
However, the mitochondrial cytochrome b data that included GenBank sequences from the
type locality in Kenya suggest that A. wilsoni may not be monophyletic. Ecologically, the
two species seem to partition their niches with A. cf. percivali being found in well-covered
habitats with thorn bushes, rocky and mountainous areas, and A. wilsoni being found in
open semi-arid grasslands as well as in rice fields. The two species appear to be isolated by
complex natural barriers formed by the Great East African Rift Valley whose geological
features have generally been associated with active rodent speciation. However, the present
results need further multidisciplinary investigation involving extensive sampling and
examination of topotypical material.
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Keywords
Spiny mice, Geometric morphometric, Complex natural barriers, Acomys I. Geoffroy, Northen Tanzania