[The mountain weasel Mustela kathiah (Carnivora: Mustelidae): molecular and karyological data].

The karyotype of Mustela kathiah was first described. Its structure is most similar to the karyotype of M. altaica, differing inthe morphological peculiarites of five pairs of large chromosomes. A comparative analysis of mitochondrial genes in the species Mustela allowed us to clarify understanding of the place of M. kathiah in the system of the genus. The earlier hypothesized proximity of the species to a group of small weasels (altaica, nivalis) or to a group of South Asian species (strigidorsa, nudipes) was not confirmed. A high level of differences between M. kathiah of Vietnam and specimens from southern China in nucleotide sequences of the cytochrome b (7.7%) and ND2 (6-6.2%) genes was found. Perhaps these differences, manifested in populations of M. kathiah from different regions, are adaptive.

Karyotype reorganisation in the subtilis group of birch mice (Rodentia, Dipodidae, Sicista): unexpected taxonomic diversity within a limited distribution.

Conventional cytogenetic studies of Sicista subtilis and S. severtzovi (Dipodidae, Sicistinae), both attributable to the subtilis group of birch mice, revealed extensive karyotype diversity with 2n = 16-26 and NFa values of 26-46 indicating the overwhelming non-Robertsonian nature of chromosomal reorganization in these species. The numerical and structural chromosome variability was principally found in specimens located within a confined region of the East European (Russian) Plain. The approximately 135,000-km(2) area occurs in the vicinity of the Don River bend between 49°13'N/43°46'E and 51°32'N/36°16'E. The detection of cytotypes sharing similar 2n and NF values, but having morphologically distinct chromosomes, suggests that these may result from polymorphisms present both within recognized species and in cryptic taxa not hitherto described. We conducted a comprehensive, comparative chromosome banding analysis of 52 birch mice (21 localities) referable to the subtilis group and report the presence of 5 distinct karyotypes, each characterized by a combination of stable, variable, and partly overlapping 2n/NFa values. These karyotypes differed from each other by 10-29 structural chromosomal rearrangements (18.1 ± 6.3) that comprised Rb fusions/fissions (42.2%), pericentric inversions (31.1%), and tandem translocations (22.2%). The composition, and the high numbers of these chromosomal changes, is likely to provide an effective means of post-mating isolation, suggesting that taxonomic diversity within the subtilis group is larger than currently accepted. Additionally, we report the frequent fixation of tandem translocations in sample populations, one of which was found in a polymorphic state representing, as far as we are aware, the first case of an in statu nascendi tandem fusion in wild populations. Moreover, our data revealed that bi-armed chromosomes were involved in fusions detected in some of the subtilis taxa. In each instance, however, fusions were preceded by pericentric inversions that transform one or both bi-armed chromosomes into acrocentrics resulting in either centromere-telomere or Robertsonian translocations. Finally, a phylogenetic scenario inferred from a cladistic analysis of the chromosomal data suggests that the extensive karyotypic diversification within the subtilis group in the south-east region of the Russian Plain most likely results from fragmentation of a continuously distributed, ancestral population. It is thought that this occurred at the last glacial maximum (18,000-14,000 years B.P.), and that the process of isolation has been exacerbated by increasing human activity in the region in modern times.

Phylogenetic position of the saola (Pseudoryx nghetinhensis) inferred from cytogenetic analysis of eleven species of Bovidae.

Previous morphological and molecular analyses failed to resolve the phylogenetic position of the critically endangered saola (Pseudoryx nghetinhensis) with respect to its placement in Bovina (cattle, bison, and yak) or Bubalina (Asian and African buffaloes). In the present study, G- and C-banding, Ag-staining and FISH with 28S and telomeric probes was undertaken for 17 bovid species. An analysis of these data allowed us to identify 49 structural rearrangements that included autosomes, gonosomes and 17 different NOR sites. The combined data set was subjected to a cladistic analysis aimed at: (i) providing new insights on phylogenetic relationships of the saola and other species within the subfamily Bovinae, and (ii) testing the suitability of different classes of chromosomal characters for phylogenetic reconstruction of the family Bovidae. The study revealed that nucleolar organizing regions (NORs) are phylogenetically informative. It was shown that at least one, or sometimes two of these characters punctuate divergences that include nodes that are the most basal in the tree, to those that are the most recent. In this context, the shared presence of three NORs in saola and species of Syncerus and Bubalus strongly suggests the saola's placement within the subtribe Bubalina. This contrasts with Robertsonian rearrangements which are informative only at the generic level. These findings suggest that NORs are an important and frequently overlooked source of additional phylogenetic information within the Bovidae that may also have applicability at higher taxonomic levels, possibly even for Pecora.

Systematics and phylogeny of West African gerbils of the genus Gerbilliscus (Muridae: Gerbillinae) inferred from comparative G- and C-banding chromosomal analyses.

Comparative analysis of the G- and C-banding patterns in six morphologically similar species of the genus Gerbilliscus(G. gambianus, G. guineae, G. kempi, Gerbilliscus sp., G. robustus and G. leucogaster) and one belonging to the genus Gerbillurus (G. tytonis) from 27 West, East and South African localities was carried out. Our study revealed that 17 rearrangements comprising seven fissions, five translocations and five inversions occurred in the evolution of this group, with 1-13 rearrangements differentiating the various species. In addition the unusually large sex chromosomes appear to be species-specific as judged by size and morphology reflecting structural rearrangements as well as the variable presence of a large amount of C-heterochromatin found in each species at a particular chromosomal location. These karyotypic features allow us to recognize five distinct species in West Africa (compared to the two recognized in recent taxonomic lists) and to roughly delimit their geographical distributions. The pattern of phylogenetic relationships inferred from a cladistic analysis of the chromosomal data is in good agreement with recent molecular phylogenetic studies that recognize a West African species group within the genus Gerbilliscus, and the monophyly of both Gerbilliscus and Gerbillurus.

Unusually extensive karyotype reorganization in four congeneric Gerbillus species (Muridae: Gerbillinae).

Comparative analysis of the G- and C-banding patterns in four morphologically poorly differentiated Gerbillus species (G. pyramidum, G. perpallidus, G. tarabuli and G. occiduus) was carried out. These gerbils have similar karyotype morphology with 2n and NF equal to 38/76, 40/76, 40/78 and 40/80, respectively. Our study revealed that possibly 70 Robertsonian (Rb) fusions, two pericentric inversions, one tandem translocation and at least 13 non-identified rearrangements have occurred during the karyotypic evolution of these species. The number of chromosomal changes by which any of these species differ from each other ranges from 33 to 49. One Rb fusion was common to two of the species, with only a single autosome-gonosome translocation shared by all four, suggesting a monophyletic origin of these karyotypically highly divergent species. Based on the chromosomal data obtained here, the systematic and geographic implications for these North African species are also discussed.

Chromosomal characterization of Arvicanthis species (Rodentia, Murinae) from western and central Africa: implications for taxonomy.

A chromosome study of unstriped grass rats of the genus Arvicanthis (Rodentia, Murinae) in western and central Africa is presented. The observations extend the data available to 242 specimens from 59 localities. All individuals karyotyped belong to four karyotypic forms, or cytotypes, earlier described as ANI-1, ANI-2, ANI-3, and ANI-4 and are presumed to correspond to four distinct species. In order to provide diagnostic characters for these western and one central African Arvicanthis species, we standardized the chromosomal data available and developed a G- and C-banded chromosome nomenclature that allows easy species identification. Each form is characterized by a distinct geographical distribution, roughly following the biogeographical domains of western Africa, although their precise limits remain to be assessed. The sole area of sympatry detected is the region of the inner delta of the Niger River, where both ANI-1 and ANI-3 can be found. It is proposed that the three western African species ANI-1, ANI-3, and ANI-4 be renamed as A. niloticus, A. ansorgei, and A. rufinus, respectively.

Patterns of karyotype evolution in complexes of sibling species within three genera of African murid rodents inferred from the comparison of cytogenetic and molecular data.

Here we report on the analysis of three rodent sibling species complexes belonging to the African genera Arvicanthis, Acomys and Mastomys. Using cytogenetic and molecular approaches we set out to investigate how karyotype and molecular evolution are linked in these muroid sibling species and, in particular, to what extent chromosomal changes are relevant to cladogenic events inferred from molecular data. The study revealed that each complex is characterized by a distinct pattern of karyotype evolution (karyotypic orthoselection), and a specific mutation rate. However we found that the general pattern may be considerably modified in the course of evolution within the same species complex (Arvicanthis, Acomys). This observation suggests that karyotypic orthoselection documented in numerous groups is not so much a reflection of selection of a definite type of chromosomal mutation, as suggested by the classical concept, but is due to genome structure of a given species. In particular, karyotypic change appears related to the quantity and chromosomal location of repeated sequences. The congruence between the chromosomal and molecular data shows that chromosomal changes are often valuable phylogenetic characters (Arvicanthis and Mastomys, but not Acomys). However, most importantly the approach underscores the value of incorporating both in order to gain a better understanding of complex patterns of evolution. Moreover, the fact that every cladogenetic event in Mastomys is supported by two pericentric inversions allowed us to hypothesize that genetic differentiation is initiated by the suppression of recombination within inverted segments, and that the accumulation of multiple pericentric inversions reinforces genetic isolation leading to subsequent speciation. Finally, the low sequence divergences distinguishing karyotypically distinct sibling species within Arvicanthis and Mastomys emphasizes the power of combining cytogenetic and molecular approaches for the characterization of unrecognized components of biodiversity.

Comparative chromosome banding analysis of three South American species of rice rats of the genus Oryzomys (Rodentia, Sigmodontinae).

Comparative G- and C-banding analysis in three species of rice rats, namely Oryzomys megacephalus from Peru and French Guiana, O. yunganus (Peru) and O. nitidus (Bolivia) was carried out. It revealed that Peruvian O. megacephalus (2N = 52, NFa = 62) and that from French Guiana (2N = 54, NFa = 64) differ from each other by one Rb translocation and one heterochromatic arm addition/deletion. Three further Rb translocations separate them from O. yunganus (2N = 58, NFa = 62). Only 16 out of 39 autosomal pairs of O. nitidus (2N = 80, NFa = 86) shared homologous banding patterns with O. yunganus, 4 of which were involved in tandem translocations to form the larger chromosomes in two other taxa. The study suggests that O. megacephalus, O. yunganus and O. laticeps studied previously form a monophyletic group in good agreement with earlier molecular and morphological data. By contrast, the limited homologous banding patterns found between them and O. nitidus cast doubt on its belonging to the same phylogenetic lineage. In the light of available chromosomal and molecular data, the significance of intra- and interspecies karyotypic variability within Oryzomys and its relevance to systematics and phylogeny of the genus are discussed.

[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.

Robertsonian polymorphism, B chromosomes variation and sex chromosomes heteromorphism in the african water rat Dasymys (Rodentia, Muridae).

Chromosome banding analysis (G- and C-bands) of Dasymys rufulus from Senegal, Mali and the Ivory Coast, and D. cf. incomtus from Eastern and South-western Ethiopia was carried out. The diploid numbers (2N) in the former species range between 36 and 39 due to the presence of 0-3 small biarmed heterochromatic B chromosomes, resulting in a corresponding variation of the number of autosomal arms (NFa) between 44 and 50. The basic autosomal set was, however, constant and identical in these specimens. The karyotypes of D. cf. incomtus from Eastern and Western Ethiopia were found to be different (2N = 40 and 38, respectively). Comparison of G-banding patterns of the species studied revealed that they differ from each others by 1-2 Rb fusions/fissions, one paracentric inversion and heteromorphous sex chromosomes resulting from addition/deletion of heterochromatic blocks (X) and pericentric inversion (Y). In the light of the available chromosome banding data, the significance of intraspecies karyotypic variability within D. cf. incomtus and its relevance to the systematics of the genus are discussed.

Comparative chromosome banding of two South-American species of rice rats of the genus Oligoryzomys (Rodentia, Sigmodontinae).

Comparative analysis of G- and C-banding patterns in two species of pygmy rice rats, namely Oligoryzomys microtis from Peru (Ucayali and Loreto departments) and O. flavescens from Bolivia (Tarija department) established that the diploid number of the former species is 64 (NFa = 66), whereas, in the latter, it varies between 64 and 66 (NFa = 66-68) due to the presence of 0-2 heterochromatic supernumerary or B chromosomes. The G-banding pattern of the euchromatic part of their karyotypes is similar in spite of differences in morphology of the largest and smallest autosomal pairs caused by a centromeric shift and the presence of heterochromatic arms, respectively. In addition, the total quantity of C-heterochromatin is smaller in the karyotype of O. microtis than in that of O. flavescens, resulting in differences in the number and size of chromosome pairs (including sex chromosomes) bearing C-blocks. It follows from present and previous data that these karyotypic features are stable in each of these species and thus may be used as species-specific markers.

[High allozyme variation in populations of three spiny rat species from Upper Amazonia: association with ecology and evolution]. / Vysokaia allozimnaia izmenchivost' v populiatsiiakh trskh vidov shchetinistykh krys Verkhnei Amazonii: sviaz' s ékologiei i i évoliutsiei.

The allozyme variation in three spiny rat species of the genus Proechimys from Upper Amazonia was studied in relation to their ecology and evolution. The ecological environmental factors and biotopic distribution of species were analyzed. The unusually high allozyme variation was found in P. simonsi and P. sp. (2n = 34) inhabiting native forest biotopes. A relatively low allozyme variation in P. brevicauda was assumed to be associated with eurybiotic properties and the ability of this species to adapt to anthropogenic biotopes. Data on chromosome homeology and reconstruction of chromosome rearrangements in six spiny rat species were correlated with allozyme variation. The results suggested that chromosome rearrangements played the major role in evolution of the spiny rat species, and that the reorganization of the P. brevicauda genome was not random. P. simonsi and P. sp. (2n = 34), which live in native forest biotopes and carry an excessive genomik "informational load", were assumed to be highly susceptible to any novel external factors. These species are potentially able to produce new chromosome forms and are most significantly affected by deforestation.

[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.

[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.

[Comparative cytogenetics of three species of South American field hamsters of the genus Akodon (Rodentia, Cricetidae)]. / Sravnitel'naia tsitogenetika trekh vidov iuzhnoamerikanskikh polevykh khomiachkov roda Akodon (Rodentia, Cricetidae).

A karyological analysis of three species of South American field mice of the genus Akodon from four different localities of the Department of Tarija, Bolivian Republic, was performed. In Akodon simulator, 2n = 40 - 42, NFa = 42. The variation of the diploid number is caused by a polymorphism of the Robertsonian type involving six pairs of acrocentric chromosomes. Five variants of karyotypes were revealed. The chromosome set of A. sp. has 2n = 36, NFa = 40; in A. toba, 2n = 42 - 43, NFa = 44 - 46. The variation of the diploid number and the number of autosomal arms is caused by the polymorphism of the first autosomal pair. A comparative karyological analysis of A. simulator, A. sp., and A. toba revealed a high level of similarity of all karyotypic elements. Fifteen autosomal pairs of these three species have identical G-banding patterns; the others are involved in formation of larger chromosomes, representing one possible combination of the same chromosomal material. The set of rearrangements is limited only to tandem chromosome fusions.

[Chromosome differentiation of spiny rats of the genus Proechimys (Rodentia, Echimyidae)]. / Khromosomnaia differentsiatsiia shchetinistykh krys roda Proechimys (Rodentia, Echimyidae).

Karyological analysis of spiny rats of the genus Proechimys revealed four chromosome forms: 2n = 30; 2n = 29; 2n = 28; 2n = 24. 30-chromosome spiny rats are characterized by unique karyotype constitution. 27-chromosome spiny rats from the territory near Iquitos differ from the same of Pucalpa (Ucayali Department) by Y-chromosome structure and banding of long arms with two pairs of autosomes. 24-chromosome rats from the regions mentioned above do not differ in G-banded chromosomes. Diploid chromosome set equal to 29, has a family originated from the parents which had 2n = 30 and 2n = 28 under the laboratory conditions. The absence of clear morphological differentiation, similarity of constituent parts of the karyotype and hybridization possibility point to relatively recent origination of the chromosome forms under study.