27 research outputs found
Between the Balkans and the Baltic : phylogeography of a common vole mitochondrial DNA lineage limited to Central Europe
The common vole (Microtus arvalis) has been a model species of small mammal for studying
end-glacial colonization history. In the present study we expanded the sampling from
central and eastern Europe, analyzing contemporary genetic structure to identify the role of
a potential `northern glacial refugium', i.e. a refugium at a higher latitude than the traditional
Mediterranean refugia. Altogether we analyzed 786 cytochrome b (cytb) sequences (representing
mitochondrial DNA; mtDNA) from the whole of Europe, adding 177 new sequences
from central and eastern Europe, and we conducted analyses on eight microsatellite loci for
499 individuals (representing nuclear DNA) from central and eastern Europe, adding data
on 311 new specimens. Our new data fill gaps in the vicinity of the Carpathian Mountains,
the potential northern refugium, such that there is now dense sampling from the Balkans to
the Baltic Sea. Here we present evidence that the Eastern mtDNA lineage of the common
vole was present in the vicinity of this Carpathian refugium during the Last Glacial Maximum
and the Younger Dryas. The Eastern lineage expanded from this refugium to the Baltic and
shows low cytb nucleotide diversity in those most northerly parts of the distribution. Analyses
of microsatellites revealed a similar pattern but also showed little differentiation between
all of the populations sampled in central and eastern Europe
Elastic Theory of Defects in Toroidal Crystals
We report a comprehensive analysis of the ground state properties of
axisymmetric toroidal crystals based on the elastic theory of defects on curved
substrates. The ground state is analyzed as a function of the aspect ratio of
the torus, which provides a non-local measure of the underlying Gaussian
curvature, and the ratio of the defect core-energy to the Young modulus.
Several structural features are discussed,including a spectacular example of
curvature-driven amorphization in the limit of the aspect ratio approaching
one. The outcome of the elastic theory is then compared with the results of a
numerical study of a system of point-like particles constrained on the surface
of a torus and interacting via a short range potential.Comment: 24 pages, 24 figure
An Assessment of the Systematics of the Genus Desmomys Thomas, 1910 (Rodentia: Muridae) Using Mitochondrial DNA Sequences
Testing of alternative hypotheses for speciation: A case study on ground vertebrates in tropical mountains
Species composition, distribution and habitat association of rodents from Arbaminch forest and farmlands, Ethiopia
Multiple radiations of spiny mice (Rodentia: Acomys) in dry open habitats of Afro-Arabia: evidence from a multi-locus phylogeny
Abstract Background Spiny mice of the genus Acomys are distributed mainly in dry open habitats in Africa and the Middle East, and they are widely used as model taxa for various biological disciplines (e.g. ecology, physiology and evolutionary biology). Despite their importance, large distribution and abundance in local communities, the phylogeny and the species limits in the genus are poorly resolved, and this is especially true for sub-Saharan taxa. The main aims of this study are (1) to reconstruct phylogenetic relationships of Acomys based on the largest available multilocus dataset (700 genotyped individuals from 282 localities), (2) to identify the main biogeographical divides in the distribution of Acomys diversity in dry open habitats in Afro-Arabia, (3) to reconstruct the historical biogeography of the genus, and finally (4) to estimate the species richness of the genus by application of the phylogenetic species concept. Results The multilocus phylogeny based on four genetic markers shows presence of five major groups of Acomys called here subspinosus, spinosissimus, russatus, wilsoni and cahirinus groups. Three of these major groups (spinosissimus, wilsoni and cahirinus) are further sub-structured to phylogenetic lineages with predominantly parapatric distributions. Combination of alternative species delimitation methods suggests the existence of 26 molecular operational taxonomic units (MOTUs), potentially corresponding to separate species. The highest genetic diversity was found in Eastern Africa. The origin of the genus Acomys is dated to late Miocene (ca. 8.7 Ma), when the first split occurred between spiny mice of eastern (Somali-Masai) and south-eastern (Zambezian) savannas. Further diversification, mostly in Plio-Pleistocene, and the current distribution of Acomys were influenced by the interplay of global climatic factors (e.g., Messinian salinity crisis, intensification of Northern Hemisphere glaciation) with local geomorphology (mountain chains, aridity belts, water bodies). Combination of divergence dating, species distribution modelling and historical biogeography analysis suggests repeated “out-of-East-Africa” dispersal events into western Africa, the Mediterranean region and Arabia. Conclusions The genus Acomys is very suitable model for historical phylogeographic and biogeographic reconstructions of dry non-forested environments in Afro-Arabia. We provide the most thorough phylogenetic reconstruction of the genus and identify major factors that influenced its evolutionary history since the late Miocene. We also highlight the urgent need of integrative taxonomic revision of east African taxa