Molecular systematics and biogeographic history of the African climbing-mouse complex (Dendromus).

Climbing mice in the genus Dendromus (sensu lato) are widely distributed in Africa, south of the Saharan Desert. The 17 currently recognized species in the genus range from widespread taxa to single-mountain endemics, and there is considerable variation across species with respect to habitats occupied. These habitats range from arid grasslands and savannahs to sub-alpine and alpine vegetation. Using the most comprehensive geographic and genetic survey to date and after reviewing many type specimens, we assess the systematics and biogeography of Dendromus. Given the structure of our molecular phylogenetic hypotheses, in which we recover six major clades, we propose the recognition of three genera within the Dendromus group (sensu lato): in addition to Dendromus (26 lineages), we suggest the retention of Megadendromus (monotypic) and the resurrection of the genus Poemys (six lineages). From our model-based molecular phylogenetic results and morphological comparisons, we suggest that six formerly synonymized taxa should be resurrected, and we highlight 14 previously undescribed lineages. We also constructed time-calibrations on our phylogeny, and performed ancestral area reconstructions using BioGeoBEARS. Based on fossil evidence, Dendromus appears to have had a widespread African distribution dating back to the Late Miocene (8-10 Ma), and our basal ancestral area reconstruction (Ethiopians Highlands + Eastern African Mountains + Zambezian region) supports this. Divergence of the six major clades we recover (Poemys, Megadendromus and four within Dendromus) occurred prior to or at the Miocene-Pliocene boundary 5.3 Ma. Biogeographically, Megadendromus is restricted to the Ethiopian Highlands. The ancestral area for Poemys is reconstructed as the Zambezian region, with species distributions ranging from South Africa to Western Africa. The ancestral area for Dendromus is reconstructed as the Ethiopian Highlands, with the ancestral areas of the four major clades being reconstructed as Ethiopian Highlands, Albertine Rift, South Africa or Western Africa. None of the four Dendromus clades are reciprocally monophyletic with respect to distributional area.

Multiple radiations of spiny mice (Rodentia: Acomys) in dry open habitats of Afro-Arabia: evidence from a multi-locus phylogeny.

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.

Morphological Variability of the Mandible Shape of the Common Vole Microtus arvalis (Rodentia, Arvicolidae) Semi-species from the Hybrid Zone.

The mandible shape of the common vole semi-species from the hybrid zone was studied for the first time using the methods of geometric morphometry. The hybrid specimens were found to display high morphological variability being closer to the parental Microtus obscurus than to M. arvalis form. The main trends of changes in the mandible shape were primarily observed in the horizontal plane.

Adaptation of Rodents Living in a Highland: Combination of Mitochondrial Introgression and Convergent Molecular Evolution.

Populations of four species of narrow-headed rats of the genus Stenocephalemys were examined for the presence of a mutation in the mitochondrial cytochrome b gene resulting in an amino acid substitution in the translated protein. This substitution was also found in hamsters of the subfamily Sigmodontinae inhabiting the highlands of the Andes. Simulation of three-dimensional structure of the protein showed that this substitution is located in the active site and may have a functional significance. We assumed an independent emergence of this substitution in the populations of two Afroalpine species of Stenocephalemys, which is the first known example of a combination of introgression and convergent molecular evolution.

A decrease in heat insulation of the black-clawed brush-furred rat (Lophuromys melanonyx, Petter) during adaptation to high altitudes.

The results of the body-surface infrared thermography of rodents of the genus Lophuromys suggest that heat insulation of the black-clawed brush-furred rat L. melanonyx, a large specialized species of the AfroAlpine zone, is worse than that of the related smaller species, the golden-footed (L. chrysopus) and shorttailed (L. brevicaudus) brush-furred rats, that inhabit tropical forest and Erica shrub, respectively. A decrease in heat insulation of the alpine species may facilitate the use of solar radiation for supporting heat balance of these diurnal animals.

[The role of hybrid zones in speciation: a case study on chromosome races of the house mouse Mus domesticus and common shrew Sorex araneus].

Although diverse complexes of chromosome races are of rather rare occurrence in mammals, that does not reduce its importance to insignificant phenomenon not worthy of studying as some unique case without direct analogy. Moreover, these complexes present virtually ideal models for estimation of the impact of hybridization on the process of microevolution. The chromosome races are characterized by almost zero level of genetic differentiation and well-defined distinctions, usually induced by chromosome rearrangements only. The presented review shows the valuable contribution of the studies on Sorex araneus and Mus domesticus chromosome Robertsonian systems into our understanding of varied impacts of hybridization on the speciation process. Particularly, it promotes better understanding of such evolutionary phenomena as "reinforcement" of reproductive isolation in secondary contact zones between divergent populations, speciation without geographic separation ("divergence with gene flow"), and "zonal raciation".

[Molecular cytogenetic markers of cryptic species and hybrids of the common vole superspecies complex Microtus arvalis s. l].

Molecular markers of cryptic cytogenetical differentiation were shown in chromosomal polymorphic Pan-European model group of rodents Microtus arvalis s. l. by FISH analysis. The polytypy of 46-chromosomes karyotypes determined by the sites of interstitial telomeric sequences (ITS) and ribosomal DNA emphasizes the genetical isolation of M. arvalis s. s. and M. obscurus.

[Testing of alternative hypotheses for speciation: a case study on ground vertebrates in tropical mountains].

Empirical testing of the hypotheses for speciation, namely, allopatric (refugia model) and parapatric (gradient model) models, has been attempted using molecular phylogenetic methods by a case study on several groups of closely related species of small mammals inhabiting the Ethiopian Plateau. Comparison of the results with the available literature data on other ground vertebrates of tropical mountains has allowed us to demonstrate groundlessness of the currently popular concept on the significant role of parapatric speciation in formation of modern tropical biodiversity. It has been shown that a marked partition of altitudinal gradient by relatively close ground vertebrate species of tropical mountains in the majority of cases is secondary in nature and is not connected with the specific mode of their origination.

[Genomic versus chromosomal polytypy in studies of mitochondrial and nuclear DNA markers in the Microtus arvalis group].

Common voles of the Microtus arvalis group distributed over the territory of European Russia are represented by three karyotypic categories, i.e., sympatric sibling species with 2n = 46 and 54, and two allopatric karyoforms in one of them, 2n = 46. For each category, molecular markers were found. For two 46-chromosome forms (arvalis and obscurus), DNA was for the first time studied in karyotypes and non-karyotyped specimens for a parapatric hybrid zone, where high diversity of intermediate karyotypes was recorded. Preferential migration of the mitochondrial markers in arvalis and significant differences in the cline width for chromosomal and nuclear markers in obscurus were shown. The hybrid zone examined exhibited unusual combination of such features as the practically complete absence of "pure" representatives of the original parental forms and a clear deficiency of the first generation hybrids. The mtDNA divergence for the arvalis and obscurus karyogroups (4.6%) is comparable to the lowest limit for interspecies differences within the large and complex genus Microtus.

[Cytogenetic study of the parapatric contact zone between two 46-chromosomal forms of the common vole in European Russia].

Since the first description of sympatric sibling species and allopatric chromosomal forms of the common vole (Microtus arvalis group) in 1969, the search of their range boundaries has been Continually going on up to the present time. Based on the cytogenetic material presented in the present study, the geographical distribution of two karyoforms (2n = 46: NF = 84 and NF = 72) was examined in 20 geographic localities of European Russia (within the interval between the longitude 34 degrees-56 degrees East and 51 degrees-61 degrees). The places of findings of two karyoforms, "arvalis" and "obscurus", in Russia have been supplemented and were shown to be significantly closer; whereas the well-known distribution boundaries for the "obscurus" form were specified in the northern and southern parts of Russia.A direct evidence of parapatric distribution and hybrid zone formation between the "arvalis" and "obscurus" karyoforms was obtained, which suggests the possibility of studying the evolutionary relations ships between two genomes in the Russian part of the group range under the natural experimental conditions-the hybrid zone at the boundary between the "arvalis" and "obscurus".

[Evolutionary relationships among narrow-headed rats (genus Stenocephalemys, Muridae, Rodentia) inferred from complete cytochrome b gene sequences].

Using the data on complete sequences of cytochrome b gene, phylogenetic relationships were studied among the Stenocephalemys s. lat. (Stenocephalemys ssp. + Praomys albipes) murine rodents, inhabiting adjacent altitudinal belts of the isolated Ethiopian mountain massifs, and among the related Praomys s. lat. species. Extremely low resolution of the relationships among the main Praomys s. lat. lineages hampered identification of the nearest sister group for the Stenocephalemys s. lat. "Ethiopian" clade, monophyly of which was strongly supported. Sister relationships between P. albipes and S. griseicauda (implying "accelerated" morphological and chromosomal evolution upon the formation of the former species), as well as between S. albocaudata and the recently described novel chromosomal form of Stenocephalemus sp. A (2n = 50; NFa = 56) were demonstrated. Definite discordance between the rates of their molecular, chromosomal, and morphological evolution was revealed. Based on phylogenetic reconstructions and the estimates of the divergence time, obtained by use of molecular clock method, an attempt to draw a phylogenetic scenario for the group examined was made. The obtained data were compared to those for analogous Sigmodontinae species complexes, distributed across a marked altitudinal gradient on the Andean slopes. It was shown that molecular genetic data on the rodents from mountain tropics did not support the gradient model of diversification, based on the possibility of morphological diversification prior to their achievement of the species status (without interruption of the gene flow between the forms) due to differently directed selection across a strong environmental gradient.

[Origin of the house mice (superspecies complex Mus musculus sensu lato) from the Transcaucasian region: A new look at dispersal routes and evolution]. / Proiskhozhdenie domovykh myshei Zakavkaz'ia (nadvidovoi kompleks Mus musculus). Novyi vzgliad na puti ikh rasseleniia i évoliutsiiu.

We analyzed our results and literature evidence on variability of nuclear protein genes in 39 populations of eight synanthropic and wild species of house mice (superspecies complexes Mus musculus and M. spicilegus) from Transcaucasia, Eastern and Western Europe, Near and Middle East, Central, South, and East Asia, and Cuba. These data were for the first time ever combined into a single database by unification of nomenclature of 21 loci examined by different authors in 39 populations. Analysis of geographical allele distribution have shown that populations of domestic Transcaucasian mice are close to Indo-Pakistani populations of form oriental of the species M. castaneus, which preserved a high level of ancestral polymorphism. We concluded that a very heterogeneous, rich gene pool of house mice from Transcaucasia could not develop only by secondary contacts of differentiated M. musculus s. str. and M. domesticus forms, since it is similar to the ancestral gene pool of the superspecies complexes M. musculus and M. spicilegus. In this context, unique characteristics of some Central Asian populations were examined; these populations may have served as a "transit station" in the dispersal of synanthropic house mice forms. We suggest that the Transcaucasian populations are genealogically closely related to an early Near East form of M. musculus, which, as M. domesticus and M. castaneus, split from the common ancestor and preserved nondifferentiated pool of ancestral alleles of protein genes. This hypothesis admits the involvement of differentiated species M. musculus s. str. and M. domesticus in the ultimate formation of the gene pool of Transcaucasian house mice. Apparently, these populations resulted from alternation and (or) "overlapping" of different evolutionary processes. A scenario suggesting that hybrid events having occurred in Transcaucasia at different times, were "superposed" on the gene pool of the ancient autochtonous population of house mice from this region seems most plausible. Analysis of allozyme variability in the modern Transcaucasian Mus populations could not always distinguish between ancestral polymorphism and hybridization consequences.

[Analysis of allozyme variability in populations of three species of brush-haired mice of species Lophuromys (Rodentia, Muridae) from the Bale Mountains National Park in Ethiopia]. / Analiz allozimnoi izmenchivosti v populiatsiiakh trekh vidov zhestkovolosykh myshei roda Lophuromys (Rodentia, Muridae) natsional'nogo parka bale Efiopii.

Allozyme variability was examined in populations of three endemic species of the species complex Lophuromys flavopunctatus sensu lato: L. chrysopus, L. brevicaudus, and L. melanonyx. These species substitute each other in adjacent latitudinal belts of the Bale Massif in Ethiopia. A deficit of heterozygotes at several loci was found in most samples of all species studied. Moreover, the samples included animals homozygous for two or three minor alleles and heterozygous for alleles that are rare and unique for the given species. It is suggested that the Bale Massif are inhabited by numerous genetically isolated populations of each Lophuromys species, which exchange genes at an extremely low rate. Genotypic disequilibrium observed in most samples is explained by the fact that most sampling localities comprise ranges of two and more micropopulations. In our view, microgeographic subdivision of the populations is caused by recurrent fragmentation of habitats during the Pleistocene glaciation of the Bale Massif and subsequent prolonged isolation of local populations. Gene drift accompanying these processes resulted in high genetic differentiation of the local populations, which probably persisted until the present. Geographical isolation of the Bale Massif, its uniquely diverse ecological conditions, and extraordinary allozyme structure of the Lophuromys populations suggest that these populations represent remnants or direct descendants of relic local populations.

[Karyological differentiation of three species of coarse-haired mice of the genus Lophuromys (Murinae, Rodentia) from the Bale Mountain National Part in Ethiopia]. / Kariologicheskaia differeentsiatsiia trekh vidov zhestkovolosykh myshei roda Lophuromys (Murinae, Rodentia) natsional'nogo parka Bale, Efiopiia.

Three karyotypically differentiated species of harsh-furred mice, Lophuromys melanonyx (2n = 60, NFa = 90; 24m,sm + 8st + 26a + Xm + Ya), Lophuromys sp. A (2n = 54, NFa = 60; 8m,sm + 44a + Xa + Ya), and Lophuromys sp. B (2n = 68, NFa = 78; 8m,sm + 4st + 54a + Xst + Ya), were found at the Bale Mountains National Park, Ethiopia. Comparative analysis of chromosomes showed that G-banding patterns of 2 to 17 chromosome banding patterns or chromosome arms were identical in all species. Apparently, the formation of the studied species was associated with their independent karyotypic divergence during early evolution. The results obtained indicate that the rate of karyotypic alterations is not associated with the degree of morphological differentiation in this group of species.

[Karyotypes and chromosomal differentiation of two species of the genus Tachyoryctes (Rodentia, Tachyoryctinae) from Ethiopia]. / Kariotipy i khromosomnaia differentsiatsiia dvukh vidov roda Tachyoryctes (Rodentia, Tachyoryctinae) iz Efiopii.

Karyotypes of two species of genus Tachyoryctes from four localities in the Bale Mountains National Park, Ethiopia, were analyzed. T. splendens has 2n = 48, NFa = 65-86. Variations of the autosome arm number are determined by different numbers of autosomes with additional heterochromatin arms (7-17). Karyological analysis indicated that the cytogenetic structures of T. splendens from the localities studied was unique, which might result from formation of the karyotypes optimal for the given habitats. T. macrocephalus has 2n = 50, NFa = 62. A high conservatism of the number and size of C-positive heterochromatin blocks reflects the extreme specialization of T. macrocephalus endemic for the Bale province and occupying a limited ecological niche. Homology of G-banding patterns of several chromosomes and chromosome arms demonstrated that karyotypes of T. splendens and T. macrocephalus were formed from the common ancestral karyotype through different rearrangements in some chromosomes.

[Chromosome arrangements and cytogenetic differentiation of two species of African mice of the genus Mus (Rodentia, Muridae)]. / Khromosomnye nabory i tsitogeneticheskaia differentsiatsiia dvukh vidov Afrikanskikh myshei roda Mus (Rodentia, Muridae).

Karyotypes of two African mouse species, Mus mahomet, 2n = 36, NFa = 34 (34A + XA + YA) and Mus sp. A, 2n = 34, NFa = 32 (32A + XA + YA), from five localities of the Bale Mountains National Park, Ethiopia, were analyzed. In both species all autosomes contained C-positive pericentromeric blocks. In M. mahomet, heterochromatin blocks of different chromosomes varied in size. In addition, the X chromosomes of both species contained a pericentromeric block and showed more intensive staining throughout the chromosome. The Y chromosome was two times larger in Mus sp. A than in M. mahomet and C-positive in both species. Comparative analysis of G-banding patterns revealed a similarity with respect to nine autosomes and the X chromosome. Autosome 1 of Mus sp. A was demonstrated to result from centromere-telomere fusion of two M. mahomet acrocentrics. The other five autosomes represent different linkage groups determining a specificity of the karyotypes. The karyotypes of M. mahomet and Mus sp. A were also compared with that of M. musculus. The evolution of M. mahomet and Mus sp. A karyotypes was shown to have involved structural rearrangements in 10 and 12 autosomes, respectively. The high karyological divergence confirmed molecular phylogenetic data. The cytogenetic differences T of M. musculus C from M. mahomet and Mus sp. A are high enough to different genera.

Three new karyotypes extend a Robertsonian fan in Ethiopian spiny mice of the genus Acomys I. Geoffroy, 1838 (Mammalia, Rodentia).

Three new karyotypes (2n=40, 44, 52) are described revealing what are probably new cryptic species of Ethiopian spiny mice. Two other diploid numbers have already been reported for the country (2n=36 and 68) and, overall, the five known karyotypic forms constitute a common lineage differentiated by a Robertsonian process. Such arrays of karyotypic forms are known as a 'Robertsonian fan'. This view of the situation in Ethiopian Acomys I. Geoffroy, 1838 is based on standard chromosomal morphology that reveals a constant FN (68) and needs further investigation of chromosome homology by differential staining and/or molecular cytogenetic techniques as well as further molecular phylogenetic analysis.